Improvements in Metallic Junction Boxes, and Means for Uniting Metal Conduit Tubes thereto and to each other.
Year: 1896

page_text: Date of Application, 1st Aug., 1896-Accepted, 5th Sept., 1896
CODIL DELE SPECIFICATION.
[Communicated from abroad by EDWIN TRUMAN GREENFIELD, of No. 44 Broad
Street, New York City, in the County of New York and State of New York,
United States of America, Electrician.]
Improvements in Metallic Junction Boxes, and Means for Uniting
Metal Conduit Tubes thereto and to each other.
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, 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 :-
My invention has for its chief objects, to increase the efficiency of junction
boxes for connecting the ends of conduit tubes, and to diminish the expense of
manufacture of such boxes, and of their attachments.
My invention also provides improved means for uniting metal conduit tubes to
each other.
Referring to the accompanying drawings,
Figure 1 represents in plan the interior of an electrical junction box provided
with my improved means for attaching three radiating conduit tubes thereto.
Figure 2 is a section of the same taken on line x-x, Figure 1.
Figure 2 is a perspective view of a split locking ring for locking the parts
together, and
Figure 3 is a longitudinal sectional view illustrating the application of my
improved means of uniting a pair of conduit tubes.
Metallic junction boxes provided with tubular necks adapted to receive interiorly
the ends of tubular conduit tubes are already known. It has been customary, in
the use of such junction boxes, to unite the tubular conduit tubes thereto in
various ways, but not, however, with such security as would prevent them from
being drawn out of the necks. It is true that such a union might be effected by
providing female screw-threads for the inner surface of the projecting necks of
such boxes, and corresponding male screw-threads upon the outer surfaces of the
ends of the conduit tubes, but such methods of union have heretofore been
rejected owing to the expense of screw-threading the parts. It was with a view to
providing means for uniting these parts securely together in a cheap and efficient
manner that my present invention has been devised.
According to my invention I cast junction boxes B of soft metal in moulds,
under air pressure, in a manner well understood by those skilled in metal working,
said junction boxes being provided with any desired number of necks N N N
screw-threaded on their outer surfaces, the screw-threads being formed in the
process of casting. These junction boxes are then lined with paper H treated
with insulating material; or, any preferred insulating lining may be used and
applied in any suitable manner.
FF are lugs provided with screw-holes for securing the box to the wall or
ceiling. C is a detachable cap or cover adapted to be secured to the top of the
box by screws S, or in any preferred manner. TTT are armoured conduit tubes
provided with insulating linings P, the ends of said tubes being adapted to fit
snugly within the necks N N N. R Figures 2 and 24 is a split ring of metal
adapted to fit snugly upon the outer surface of the tube T; said split ring is
cone-shaped at one end and is adapted to fit in the corresponding cone-shaped

page_text: outer end of the corresponding neck N. One such ring is applied to each tube T.
D, D, D are screw-threaded locking collars which are adapted to fit over the en ls
of the tubes T so that the inner surface of each collar will abut against the base
of the split ring R, said locking collars, with their screw-threads, being cast under
pressure in the same manner as the box 'B. E, E, E are flanged thimbles of
insulating material adapted to fit in the inner ends of the necks N so that their
free ends extend into the junction box slightly beyond the insulating lining H
thereof. In assembling the parts, the thimbles E are inserted in the manner shown
in Figure 2 into the necks N of the junction box, and the ends of the tubes T are
inserted against the flanged ends of said thimbles, the locking collars D and rings R
having first been slipped upon said tubes. The locking collars are then turned,
through the agency of a pipe wrench or otherwise into locking position, the
screw-threads on the necks N and the corresponding screw-threads in the locking
collars causing the wedge-shaped rings to force the tubes T firmly home against
the flanges of the thimbles E. With such an arrangement the wedge action of the
rings R causes the inner ends of the tubes T to be as firmly united to the junction
boxes as would be possible with screw-threads. In lieu of the rings R I sometimes
use simple wedges disposed at various points around the tubes T.
In Figure 3 I have shown the application of a modified form of my improved
locking means for uniting two armoured tubes TT through the agency of
a locking piece G and split locking rings RR. P is an insulating lining of the
locking piece G adapted to complete the insulation between the insulating
linings PP of the tubes.
In this case the ends of the locking piece G are internally screw threaded and
the split rings R, R are screw threaded externally for a part of their length. In
coupling the tubes TT the split rings R R are first slipped over the ends of the
pipes which are then pushed into the locking piece G until their ends abut.
against the insulating lining P. Each split ring R is then screwed tightly into
the piece G by means of a pipe wrench, thus effecting a firm and perfectly insulated
connection.
The insulating ring P₁ may be dispensed with if desired in which case the
picce G is made without the inwardly projecting seat for the lining P1, so that
the tubes T, T may abut each against the other and so form a continuous insulated
conduit.
The latter method of securing pipes or conduits may be used instead of that
previously described for uniting tubes to junction boxes, the necks N, N, N, being
internally instead of externally screw-threaded for the purpose, and the end of the
tube T abutting against the thimble E as before.
This invention also has equal utility in connection with concentric systems of
conductors in which the outer tube T and the junction box B constitutes a part of
the electrical conducting system. In the event of the use of my invention with
concentric systems of conductors, the outer ends of the tubes T and the inner
surfaces of the necks N should be preferably electro-plated with copper, and the
split ring R should be of copper or other good conducting metal. I prefer also to
have the locking collar D in that event of copper, for the purpose of increasing the
conductivity of the system. When used in connection with concentric systems, the
lining and thimbles E may, if preferred, be dispensed with, the interior or con-
centric conductor being a well insulated conductor.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondent, I declare that what I claim is :-
1. A junction box provided with a screw-threaded neck, a screw-threaded
locking collar and means for firmly gripping or holding a tube in place in
alignment with said neck, substantially as described.
2. A metallic junction box provided with an insulating lining and a series of
hollow screw-threaded necks, an insulating thimble for each neck extending within

page_text: the box, an armored conduit tube adapted to fit within each neck, a screw-
threaded locking collar for each neck, and a locking device controlled by the
collar, all of said parts being so arranged that when the collars are screwed home
the parts are rigidly connected, substantially as described.
3. For connecting the ends of two conduit tubes, a pair of externally screw
threaded split thimbles and an internally screw threaded collar adapted to engage
with said thimbles substantially as described.
4. The means for connecting the ends of two conduit tubes, substantially as
described with reference to Figure 3 of the accompanying drawing.
Dated this 1st day of August 1896.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.