Improvements in Joint Boxes and Switches therefor, in connection with Concentric Systems of Electrical Conductors.
Year: 1898

page_text: Date of Application, 21st Oct., 1898-Accepted, 6th May, 1899
COMPLETE SPECIFICATION.
Improvements in Joint Boxes and Switches therefor, in connection
with Concentric Systems of Electrical Conductors.
I, GEORGE WILKINSON, of No. 12, Dragon View, Harrogate, in the County
of York, Electrical 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:—
The objects of my invention are primarily to construct a joint box and switch
combined so that all the conductors may be readily accessible for testing, and in
the event of a fault, it may be located more readily than by the ordinary method
and means, and without disturbing the main circuit of the system, each set of
service or section leads being independently cut off, or the main circuit if necessary.
Further, according to my invention I provide a joint box, which may or may not
contain a switching device, but which is readily accessible for repairs, and
presents every facility for inspection and testing with the highest degree of
insulation.
Heretofore the location of faults in the systems of electric lighting and power
have been carried out by cutting large sections of the network of leads forming
such systems, out of the circuit, generally resulting in the total destruction
of a number of joint boxes, but in this invention I construct an accessible box and
jointing device, with suitable earthing arrangements, with an equal degree of
insulation but which admits of the subdivision of the network of service and
main leads so as to locate such fault, or to carry out any ordinary examination
or testing operation without destroying the insulation or injuring the box and
its fittings.
In order that my invention may be the better understood, I have appended the
accompanying two sheets of drawings in which Figure 1 Sheet 1 is a sectional
elevation of the outer and inner box with connectors, earthing and switching:
devices. Figure 2 is a corresponding plan view of the inner box with the cover
removed and Figures 4, 5, 6, 7, Sheet 2 are illustrative diagrams. Like letters of
reference indicate corresponding parts throughout the several views.
or
In carrying my invention into practice I employ an outer box A. Figure 1,
covered by a lid B, the upper centre of which is filled with cement
the like, and which is level with the pavement, 11. Ledges C
cast upon
or attached to the interior of the box A support an inner
box D holding the connections and switches. The main conduits EE carrying
the main concentric cables F F are below the inner box D as shown, and the
service cables and conduits (not shown in Figure 1) are approximately upon the
same level.
A cover G is luted into a faucet at by a wax or like sealing, and
has a handle H for ready removal. A ring of hard wood I forms a loose cover over
a plate of metal which according to the official regulations governing high tension
electric installations, and well known to electrical engineers, must be "earthed'
to prevent danger by contact when the cover G is removed. This "earthing
effected by a spring plate d which is pressed upon the plate J by a set screw e
99 is:

page_text: *
which engages into a screwed hole in the central hollow arbor K upon which
the plate
revolves by means of handles or key wards, or pins e formed upon it
or attached to it. Therefore since J is in metallic connection with the plate d
which is electrically connected to the central arbor K by the set screw c, and
said central arbor K is an integral part of the inner box D) resting upon metal
ledges C in the outer box A which is buried in the earth, the plate may be
said to be earthed." Or a looped wire may be placed under the set screw e and
carried straight to the metal conduit E and there attached, this method being
simpler to understand, but not preferable. The rotation of the plate J by the
handles or the like is intended to operate the switching arrangement. A
wood ring f forms a sheath round. the indér side of the plate J, and wood or like
pegs g connect it to the insulating disc L which may also be formed of wood or other
insulating material or substance. Said disc L is extended at its base by a metal
ring having spring tongues i upon it, or split plates, which work easily, yet with
perfect contact between the forks of the contact arms which are secured by a
clip to the barèd end of the inner conductor of the concentric cable F. Each
of these cables pass through a tapered nozzle. MM filled in with a tamping of
insulating material. The contact arms j.in connection with the inner conductor
are fixed upon a block of wood or like insulator N, and the outer conductor of the
concentric cable is in every case attached to a flange or flanges at O which terminate
in or are electrically connected with tongues or plates P for purposes of secure
attachment to the body of the box. This is effected by screwing or otherwise
fitting them to an insulating disc or plate Q a ring of hard wood or the like m
intervening between N and Q as shown.
h
It is in accordance with the concentric system of wiring to couple all the outer
conductors together, and in referring to the plan view Figure 2-Sheet 1,
F and F represent the mains, and F and F the branch service leads from the
box. The inner conductor of the concentric is coupled to the switch arrangement,
but all the outers are coupled together, it may be by a continuous metallic bar,
wire or the like, or as shown preferably divided into sections or links RK'R" Ri
so that any such link or section may be removed for local testing purposes, or to cut
out a branch lead from the circuit independently of the main circuit.
In the plan
Figure 2 Sheet 1 the holding down plates P' attached to the lower flange of the
outer concentric conductor are not shown.
The function of the divided links or plates R is only as a cut out for testing
or break and the switch is only operative during necessary inspection or repairs.
In order to render the action of the switch clearly, I have appended a plan view
Figure 3 Sheet 2, and section Figure 4, in which a very simple form of said switch
is shown, and Figures 5, 6 and 7 upon the same sheet are diagrams showing every
position thereof.
The metal rings Figures 4 and 5 carry the spring tongues i¹ which in this
case pass over the forks j, secured to the clip upon the central core of the
concentric cable F. It is immaterial whether the contact forks j make contact
inside or outside the plates hh. The diagram Figure 5 shows the position of the
switch when the main leads FF and the branch service leads FF are all
connected. Figure 6 shows the branch service leads F F disconnected, but
the main leads FF in circuit. Figure 7 shows the position when all are cut out,
and the circuits are entirely broken.
It is obvious that the simple form of switch shown by these figures may be
modified to provide efficient means for testing for insulation and the like, with the
main current still flowing the branch service alone being cut out. Or as in
Figure 7, in cases of emergency the pair of circuits may be cut out, and the
connections split up into sections so that they may be subjected to an individual
test.
In every case where wood is mentioned as an insulating medium, it is preferably
soaked, or indurated at boiling point with paraffin or like liquid insulating
substance.

page_text: I may construct a simple joint box without a switching arrangement, exactly
upon the same lines as herein before described.
my
Having now particularly described and ascertained the nature of
invention, and in what manner the same is to be performed, I declare that what
I claim is:-
First. In joint boxes for concentric systems of electrical distribution the con-
struction and arrangement of an inner sealed box resting upon ledges in the
outer box, the concentric mains being brought into said inner box through the
bottom vertically and all concentric connections thus visible when the cover is
removed substantially as herein described and shown by the appended drawings.
Second. In joint boxes for concentric electrical systems the construction and
adaptation of a switch with a superimposed earthed plate controlling the service
leads apart from the main leads substantially as herein described, and shown by
the appended drawings.
.
Third. In joint boxes for concentric electrical systems, the methods of and means
for maintaining a "live" main, while breaking the branch mains substantially as
herein described.
Fourth. In joint boxes for concentric electrical systems the method of and means
for "earthing" the top plate J, substantially as described and shown by the
appended drawings.
1090
FREDK. WALKER,
73, St. Stephen's Road, Upton Park, London, E.,
Agent for the Applicant.