Year: 1887

page_text: Date of Application, 4th June, 1837
Complete Left, 13th Oct., 1887
Complete Accepted, 15th Nov., 1887
I, ROBERT THORBURN TURNBULL of 50 Old Broad Street, in the City of London,
Engineer do hereby declare the nature of this invention to be as follows:-
This invention relates to improvements in holders for electrical incandescent
lamps, and has for its object the providing of means whereby the tendency to short
circuit across the terminals of such lamp holders is done away with.
In holders of this class as heretofore constructed the terminals have generally
consisted of two metallic springs suitably mounted in a holder of insulating material
and attached at one of their ends, or other convenient point, each respectively to one
lead or wire of the circuit, the other ends being so bent as to form a hook capable of
engaging in the looped terminals of the lamp.
In terminals so constructed it was necessary in order to give the desired degree of
flexibility that the free, or hooked, ends of the springs should project for a sufficient
distance from the face of the holder, and hence there was always more or less danger
of the free, or hooked, ends of the springs coming in contact and so establishing a
short circuit, while on the other hand shortening the springs did away with the
desired degree of flexibility.
In an incandescent lamp holder constructed in accordance with this invention the
flexibility of the long spring is fully retained while all liability to short circuit is done
away with by the means hereinafter described.
In place of mounting one end of the springs in the holder direct, I place each of
the springs, made, preferably of hard drawn brass wire, in a piece of tube whose
internal diameter is somewhat greater than the outside diameter of the spring, and
having a length somewhat less than the length of the spring. One end of the spring
is soldered to, or otherwise suitably secured in electrical contact with, one end of the
tube, while the free end projecting out of the tube has formed on it a suitable hook to
engage the looped terminal of the lamp.
By this means the spring is free to yield to any extension in its length, but the
tubes acting as guides, prevent, under any but an abnormal extension, the free ends
of the springs coming together through side play.

page_text: The tubes, made of any suitable material, but preferably of brass, are screw threaded
on their outer surface for their entire length, and are screwed for a sufficient depth
into a suitable holder of wood or other insulating material. The part of the tube
which projects beyond the surface of the holder is provided with two thin thumb-nuts.
These serve as binding screws to secure the attachment of the ends of the leads or
wires to the tubes, and may also be used to lock the tubes in the holder, the inner
nut being kept tight down on the holder so as to act as a jamh, or lock, nut.
Or the tube may be screwed, or otherwise suitably secured in, or rigidly mounted
upon, a small metallic plate at right angles to it, or it may be cast together with an
encircling collar, the attachment to the holder in either case being made by screws
passing through the plate or collar. In this case either one or two of the thin thumb
nuts may be used to secure the attachment of the end of the lead or wire to each tube
as désired.
The leads or wires may run direct to the tubes, or terminals, or they may pass
through a central aperture in the holder and branch off to the respective tubes so
ensuring that all connections shall be made outside the holder.
Dal thin i ... CT 1007
F. SEATON SNOWDON,
Agent for the Applicant.

page_text: Improvements in Holders for Incandescent Electric Lamps.
I, ROBERT THORBURN TURNBULL, of 50 Old Broad Street, in the City of London,
Engineer, do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by the
following statement :-
This invention relates to improvements in holders for electrical incandescent lamps,
and has for its object the providing of means whereby the tendency to short circuit
across the terminals of such lamp holders is done away with.
In holders of this class as heretofore constructed the terminals have generally
consisted of two metallic springs suitably mounted in a holder of insulating material
and attached at one of their ends, each respectively to one wire of the circuit, the
other ends being so bent as to form a hook capable of engaging in the looped
terminals of the lamp.
With such a method of construction it was necessary in order to give the desired
degree of flexibility that the free or hooked ends of the springs should project for a
sufficient.distance from the face of the holder, and hence there was always danger of
the free ends coming in contact and establishing a short circuit, while shortening
the springs did away with the desired degree of flexibility.
In an incandescent lamp holder constructed in accordance with this invention the
flexibility of the long spring is retained, while all liability to short circuit is done
away with by the means hereinafter described.
In place of mounting one end of the springs in the holder direct each spring, made
preferably of hard drawn brass wire, is placed in a guide tube, whose internal
diameter is somewhat greater than the outside diameter of the spring, and having a
length somewhat less than that of the spring. One end of the spring is secured in
electrical contact with one end of the tube, while the free end, projecting out of
the tube, has formed on it a suitable hook to engage the looped terminal of the
lamp.
This allows the spring to yield to any extension in its length but the tubes
acting as guides prevent, under normal strains, the free ends of the springs coming
together.
The guide tubes, preferably made of brass, are, in the simplest form of holder, screw
threaded on their outer surface for their entire length, and are screwed for a sufficient
depth into a suitable holder of insulating material, the part of the tube which projects
out of the holder being provided with two thin thumb, or hexagonal, nuts as desired.
These serve as binding screws to secure the attachment of the ends of the leads or
wires to the tubes, and may also be used to lock the tubes in the holder, the inner nut
being kept tight on the holder so as to act as a lock nut. Or the tube may be
screwed, or otherwise suitably secured in, or rigidly mounted upon, a small metallic
plate at right angles to it, or it may be cast or otherwise formed with an encircling
collar, the attachment to the holder being made by screws passing through the plate

page_text: or collar, as the case may be, one or two of the thin thumb or hexagonal nuts being
used to secure the attachment of the lead or wire to each tube as desired.
Having thus indicated the nature of my invention and shown in what manner the
same is to be carried into effect I will now proceed to more particularly describe the
same, reference being made to the accompanying drawings for that purpose.
Figure 1 shows, half in section and half in clevation an incandescent lamp holder
fitted with the simplest form of the hereinhefore described improvements, while
figures 2 and 3 show modifications of the same. In an outer metallic holder A, screw
threaded at its neck to fit any desired form of pendent or other fitting, is inserted as
shown a cylindrical block of vulcanite, or other suitable insulating material B,
provided with a central aperture C through which the leads, or wires, cd pass. These
are secured by the nuts b, b, to the guide tubes i, i, which in turn are electrically
connected at a with the springs terminating in the hooks h, h, of the terminals t, t.
These terminals consist of the brass tubes i, i, in which the springs terminating at
their free ends with the hooks h, h, are suitably secured at a.
These tubes may be
screw threaded on their outer surfaces for their entire length and screwed into the
block B as in Fig. 1, or they may as shown by Fig. 2 be provided with a base plate j
through which screws securing them to the block of insulating material would pass;
or the tubes may, as in Fig. 3, be cast, or otherwise formed with, an encircling
collar k, provided with screw holes for the same purpose. If, as in Fig. 1, the
tubes i, i, are simply screwed into the block of insulating material B, the upper nuts
may be kept screwed tight up so as to act as lock nuts, while in the modifications,
Figs. 2 and 3, only one of the nuts b, if desired, need be used, the lead or wire being
secured between it and the base plate j, or collar k, as the case may be.
It will be understood that in place of passing through the central aperture C the
leads or wires may pass direct to the tubes i, i.
Having now particularly described and ascertained the nature of my said invention,
and in what manner the same is to be performed, I declare that what I claim is: -
The method of constructing the terminals of holders for electrical incandescent
lamps by employing a guide tube to prevent the tendency to short circuiting which
otherwise exists, substantially as hereinbefore described and illustrated by Figs. 1, 2,
and 3 of the accompanying drawings.
1 1.
O
1
Ր