IMPROVEMENTS IN AND CONNECTED WITH APPLIANCES FOR CONDUCTING AND CONTROLLING ELECTRIC CURRENTS
Year: 1883

page_text: LETTERS PATENT to John Macintosh Mackay Munro, of Glasgow, in the
County of Lanark, North Britain, Electrician for an Invention of
"IMPROVEMENTS IN AND CONNECTED WITH APPLIANCES FOR CONDUCTING
AND CONTROLLING ELECTRIC CURRENTS "
PROVISIONAL SPECIFICATION left by the said John Macintosh Mackay
Munro at the Office of the Commissioners of Patents on the 5th April
1883.
JOHN MACINTOSH MACKAY MUNRO, of Glasgow, in the County of Lanark,
North Britain, Electrician, IMPROVEMENTS IN AND CONNECTED WITH APPLIANCES
"
FOR CONDUCTING AND CONTROLLING ELECTRIC CURRENTS"
This Invention has for its object to provide improved safer and otherwise better
appliances than those hitherto in use for conducting and controlling electric
currents.
When two separate wires conveying a powerful electric current and its return
current are led through a building in the ordinary way it is almost impossible to
secure perfect safety. Many insulating substances are penetrable by water or
liable to destruction by vermin, and those which are damp proof such as rubber,
guttapercha, bitumen, and the like are easily inflammable, whilst harder insulators
such as vulcanite, porcelain, fireclay and the like are easily cracked and broken
even if in clumsy masses. Wood admits moisture and like soft insulators is
attacked by vermin. Various expedients may be combined; thus the wires may
be covered with rubber against damp, and overlaid with asbestos against fire,
next placed in wood troughing to prevent the wires from being forced together or
displaced by workmen or even by rats or mice, and finally as nails may be driven
through the wood and it is otherwise liable to injury it is necessary to cover it
with stout sheet metal. Appliances so cumbersome are both expensive and in
many cases impossible to fit.
To do away with inconveniences such as have been indicated it is by this
Invention proposed to make one of the conductors hollow or tubular and to use it

page_text: as a cover and protection for the other conductor which with an insulating coating
is to be passed through it. The outer conductor is a copper or brass tube of at
least as low resistance as the inner conducting wire. The tube may be externally
polished or otherwise ornamented; but is by preference enamelled both inside and
outside. It may be insulated by the ennniel and by being carried on insulating
supports like those designed and used by the present applicant for bare wires; but
in general it will be connected to earth at one or more points, so that there will be
no danger of fire or of leakage of electricity and consequent waste of the conductors,
nor of the communication of shocks to any person who may touch the conductor,
or the electrolier switches or other parts. The inner wire should have an insulating
coating even when the outer tubular conductor is enamelled, or it may have non-
conducting rings between it and the tubular conductor. The tubular conductor
will be made in lengths which will be connected preferably by screw couplings;
and where a branch is to be joined to the inner conductor the outer tube is cut
and separated to give access. After the branch joint is made and insulated two
half T-shaped coupling pieces are applied to connect the outer tube and secured
by screwed rings or otherwise. The couplings and movable pieces are formed
with flanges or otherwise to be made watertight by cementing or in some cases by
soldering. Where a fusible plug is to be inserted the ends of the inner wire are
fitted with clips in which to place the fusible plug, and the two ends of the tubular
conductor are connected by a piece the middle of which is segmental or partly cut
away to give access to the fusible plug. A glass tube is secured over the part
with rubber rings and can be moved along to give access for replacing the fusible
plug when required the replacement being effected in a few moments.
When the conductors are to be under ground the ordinary lead-covered wire
or iron tubing may be used for the continuation of the tubular conductor, the main
return being by earth. When several wires have to be arranged together under
ground & trough is used of bitumen-saturated wood or of earthenware or metal.
A layer of bitumen is poured into it and before it is hard grooves are formed
along it by a roller. Over the grooved bitumen bitumen-saturated laths of wood
or millboard are placed and another layer of bitumen poured in. A second tier
of grooves may be formed in this second layer or the lid of the trough may be
fixed down on it. In this way a number of straight and smooth bores or channels
are formed which are perfectly watertight and in which even bare wires may be
placed and from which they can be easily withdrawn for examination and repair.
When space is an object the ridges or walls between the grooves may be made
quite thin and may be strengthened by thin wood or paper or even by rows of
metal or other pins.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John Macintosh Mackay Munro in the Great Seal Patent Office
on the 4th October 1883.
JOHN MACINTOSH MACKAY MUNRO, of Glasgow, in the County of Lanark,
North Britain, Electrician "IMPROVEMENTS IN AND CONNECTED WITH APPLIANCES
FOR CONDUCTING AND CONTROLLING ELECTRIC CURRENTS
"
My said Invention has for its object to provide improved safer and otherwise
better appliances than those hitherto in use for conducting and controlling electric
currents
When two separate wires conveying a powerful electric current and its return
current are led through a building in the ordinary way it is almost impossible to
secure perfect safety. Many insulating substances are penetrable by water or liable
to destruction by vermin; and those which are damp proof such as rubber, gutta-
percha, bitumen, and the like are easily inflammable, whilst harder insulators such
as vulcanite, porcelain, fireclay and the like are easily cracked and broken even if
in clumsy masses. Wood admits moisture and like soft insulators is attacked by
vermin. Various expedients may be combined; thus the wires may be covered
with rubber against damp, and overlaid with asbestos against fire, next placed in
wood troughing to prevent the wires from being forced together or displaced by
workmen or even by rats or mice, and finally as nails may be driven through the
wood and it is otherwise liable to injury it is necessary to cover it with stout sheet
metal. Appliances so cumbersome are both expensive and in many cases impossible
to fit.
To do away with inconveniences such as have been indicated it is by this
Invention proposed to make one of the conductors hollow or tubular and to use it
as a cover and protection for the other conductor which with an insulating coating
is to be passed through it. The outer conductor is a copper or brass tube of at least
as low resistance as the inner conducting wire. The tube may be externally
polished or otherwise ornamented; but is by preference enamelled both inside and
outside. It may be insulated by the enamel and by being carried on insulating
supports like those designed and used by the present applicant for bare wires; but
in general it will be connected to earth at one or more points, so that there will be
no danger of fire or of leakage of electricity and consequent waste of the conductors,
nor of the communication of shocks to any person who may touch the conductor, or
the electrolier switches or other parts. The inner wire should have an insulating
coating (preferably protected by tape or cloth) even when the outer tubular
conductor is enamelled, or it may have nonconducting rings between it and the
tubular conductor. The tubular conductor will be made in lengths which will be
connected preferably by screw couplings; and where a branch is to be joined to
the inner conductor the outer tube is cut and separated to give access. After the
branch joint is made and insulated two half T-shaped coupling pieces are applied
to connect the outer tube and secured by screwed rings or otherwise. The couplings
and movable pieces are formed with flanges or otherwise to be made watertight by
cementing or in some cases by soldering. Where a fusible plug or short length of
conductor is to be inserted the ends of the inner wire are fitted with clips in which
to place the fusible plug, and the two ends of the tubular conductor are connected
by a piece the middle part of which is segmental or partly cut away to give access
to the fusible plug. A glass tube is placed over the part and can be moved along
to give access for replacing the fusible plug when required the replacement being
effected in a few moments.
When the conductors are to be under ground the ordinary lead-covered wire or
iron tubing may be used for the continuation of the tubular conductor, the main

page_text: return being by earth. When several wires have to be arranged together under
ground a trough is used of bitumen-saturated wood or of earthenware or metal. A
layer of bitumen is poured into it and before it is hard grooves are formed along
it by a roller. Over the grooved bitumen, bitumen-saturated laths of wood or
millboard are placed and another layer of bitumen poured in. A second tier of
grooves may be formed in this second layer, or the lid of the trough may be fitted
down on it. In this way a number of straight and smooth bores or channels are
formed which are perfectly watertight and in which even bare wires may be
placed, and from which they can be easily withdrawn for examination and repair.
When space is an object the ridges or walls between the grooves may be made
quite thin and may be strengthened by thin wood or paper or even by rows of
metal or other pins.
My improved system of conductors with central insulated wires enclosed in metal
tubes, which latter are used for the return currents may be extended to various
fittings employed for electrical lighting, as brackets, electroliers, and their branches
may be safely used as part of the circuits. And in thus carrying out the system
improved or modified forms of switches lamp holders and other parts or connections
are required or rendered desirable. Examples of such parts are shown on the
accompanying sheet of explanatory drawings which also illustrate my improved
tube-and-wire conductors hereinbefore described.
Figure, 1, on the accompanying sheet of drawings is a longitudinal section of a
portion of a conducting wire, 12, enclosed in lengths, 13, of metal tubing, and
having a branch wire, 14, soldered or joined to it. The lengths, 13, of tubing are
united by means of screw couplings, 15, and at each branch joint there is interposed
between two screw-couplings, 15, a pair of half T-pieces, 16, one of which is
shown separately in figure, 2. The wire, 12, is first coated with rubber or other
suitable insulant, 17. and this is covered with a protecting sheath, 18, of cloth or
tape, and at the branch joint these coverings are carefully united to similar
coverings on the branch wire, 14. Figure, 3, is a section as at right angles to
figure, 1. at the branch joint.
Figures, 4, to 6, represent a convenient switch as applied to the outer conductor
or metal tube, figure, 6, being a section. Lengths 13, of the tubing are connected
by screwed couplings, 19, and an interposed piece, 20, of vulcanite or other suitable
non-conducting material. On this insulating piece, 20, there is fitted to turn a
metal ring, 21, having a handle, 22, and whilst this ring is in contact with one
screw coupling, 19, it has projecting spring blades, 23, which extend across the
insulating piece, 20, and can form contacts with projections, 24, made on the other
screw coupling, 19. In figure, 4, the parts 23, 24, are shown in contact, and in
figure, 5, which is an inverted view relatively to figure, 4, the parts 23, 24, are
shown out of contact, the movable or swith ring, 21, being turned partly round.
Figure, 7, is a section of a switch device in which the central wire, 12, is made
discontinuous and contact between the parts made or broken by means of an
external handle, 25, like that of a gas tap. The tube lengths, 13, are connected by
screw couplings and an interposed enlargement or box, 26, which may be con-
veniently made in two halves. The spindle of the handle, 25, is inserted through
the middle of the box and has fixed on it a cross piece, 27, of earthenware or
other suitable non-conducting material, which bears against the insides of spring
tongues, 28, attached to the wire ends, 12. When the handle, 25, is placed across
as shown, the crosspiece, 27, separates the tongues, 28, so as to break contact, but
when the handle is turned a quarter round or so as to be along the tubing the
tongues, 28, make contact and complete the circuit.
Figure, 9, is a partly sectioned view showing the mode of arranging my tube-
and-wire conductors at the point of suspension of an electrolier from a ceiling. A
ball-and-socket joint, 29, like that usually employed with a gasalier is fitted at the
top of the pendent tube, 13, and in the upper box of the joint, a short spiral coil, 30, E
is used to connect the central wire, 12, with the corresponding wire of the tubing, 31,
which connects the electrolier with the source of electricity

page_text: Figure, 10, is a section showing my improved arrangement for holding a safety
plug or fusible piece of conductor; in which arrangement the fusible piece, 32, is
held in clips formed in the ends of the central wire, 12. A short length, 33, of
metal tubing a little larger than the main tubing (13) is arranged to partly enclose
the fusible connection but is cut away at one side to give access, a piece of glass
tube, 34, being used to cover the fusible piece, 32, which glass tube, 34, can be
made to slide along inside of the outer metal tubing, 33, when the fusible piece, 32,
has to be adjusted or renewed. In the same figure a second form of external
switch is shown, the outer metal tube, 33, being at one end separated by a non-
conducting piece, 35, from the continuation of the plain outer tubing, 13. The
switch is a lever, 36, jointed to a ring on the end of the tubing, 13, which lever
when turned up as shown enters between a pair of spring tongues, 37, in metallic
connection with the outer tube, 33. When the lever 36, is turned down the
circuit becomes broken.
Figure, 8, is a section of an incandescent-lamp holder constructed or adapted to
suit my tube-and-wire conductors. A plug or block, 38, which forms the principal
part of the holder, and is of vulcanite or other suitable non-conducting material,
has fixed to it a metal base, 39, which can be screwed into the end of a conductor
tube (13) the central wire, 12, passing up into a metal socket, fixed in the centre
of the block, 38. After the block, 38, has been screwed home, the central wire 12,
previously loose in the socket, is gripped by means of a screw pin entered from
one side of the block. On opposite sides of the socket the block, 38, has holes
bored in it to receive spiral springs, 40, the upper ends of which are hooked to
engage with the conductors of the incandescent lamp, 41, whilst their bottom ends
are fixed and connected, one to the central socket so as to communicate with the
central wire, 12, and the other to the metal base, 39, so as to communicate with
the outer tubular conductor (13). Outside of the block, 38, there is fitted a thin
metal sheath or casing, 42, formed with three or more spring tongues, 43, which
latter grip the lower part of the incandescent lamp, 41. Slots are formed on
opposite sides of the outer casing, 42, and through these screws, 44, are fixed into
the block, 38, and serve for fixing the casing in a higher or lower position on the
block. Thus, when the conductors of the lamp, 41, have been hooked on the
spirals, 40, the casing, 42, may be pushed up until sufficient strain has been put on
the spirals to hold the lamp steadily and then the screws, 44, may be tightened up.
In this way when the lamp is to be placed where it may be subjected to
considerable vibration it may be held with adequate firmness.
Figure, 11, is a section showing another modification of incandescent-lamp
holder adapted for my tube-and-wire conductors. Like the other, this holder
consists principally of a block, 38, of vulcanite or other suitable non-conducting
material, which is fitted with wire spirals. 40, having hooked ends to engage with
the conductors of the incandescent lamp (41, not shown in this figure) The
spirals, 40, are placed horizontally and so as to give the hooked ends a tendency
to diverge; and glass beads, 45, are fixed on the wires to prevent contact taking
place when they are pressed inwards. Curved wire, 46, are fixed into opposite
sides of the block, 38, to embrace and hold the lower part of the lamp (41). The
bottom of the block, 38, has fixed on it a metal piece, 47, screwed for being
coupled to the conductor tubing, 13, and one of the wires, 40, is connected to this
piece, 47, whilst the other wire is connected to a small metal plate at the bottom
of the block, up against which there is pressed, by the screwing up of the coupling
parts, a metal button formed on the end of the central conductor wire, 12.
Having thus particularly described my said Invention and the manner of
performing the same I have to state that I do not restrict myself to the precise
details herein described or delineated but that what I believe to be novel and
original and claim as the Invention secured to me by and in terms of the herein-
before in part recited Letters Patent is :—
1. The improved system of constructing or arranging conductors for electric
currents when leading or distributing such currents through buildings or without

page_text: covering, the said system consisting principally in using metal tubing to enclose
and protect insulated wires and at the same time to serve for return currents,
substantially as hereinbefore described.
2. The improved mode of forming branch connections hereinbfore described with
reference to figures 1, 2, 3, of the accompanying drawings.
3. The combinations of parts forming the switch devices hereinbefore described
with reference to figures, 4, 5, 6, 7, 10, of the accompanying drawings.
4. The improved combination of parts for applying a fusible plug or safety
piece in a circuit, hereinbefore described with reference to figure, 10, of the
accompanying drawings.
5 The improved incandescent-lamp holders herein before described with reference
to figures 8, 11, of the accompanying drawings.
6. The formation and arrangement of troughs with grooved beds for several
wires formed by means of rollers in bitumen for holding insulating and protecting
conductors when placed under ground, combined with the accessory devices sub-
stantially as hereinbefore described.
In Witness whereof I, the said John Macintosh Mackay Munro, have hereunto
set my hand and seal this third day of October in the year of our Lord One
thousand eight hundred and eighty-three.
Witness
EDMUND HUNT
Patent Agent
Glasgow
}
J. M M MUNRO. (L.S.)