proved Means of Lessening the Danger Attendant upon the Employment of Overhead Conductors in Electric Tramways.
Year: 1899

page_text: Date of Application, 27th June, 1899
Complete Specification Left, 27th Mar., 1900-Accepted, 28th Apr., 1900
PROVISIONAL SPECIFICA
Improved Means of Lessening the Danger Attendant upon the
Employment of Overhead Conductors in Electric Tramways.
I, MICHAEL HOLROYD SMITII, of Albany Buildings, 47, Victoria Street, West-
minster, do hereby declare the nature of this invention to be as follows:-
The use of overhead conductors for electric tramways presents two dangers
to the public one mechanical one electrical; for in one case the overhead wires
might so break that the swish of the falling wire, suddenly relieved from tension,
would kill or seriously damage any living creature beneath it, or whom it struck.
In the other case a wire might break and in its fall do no damage, or be left
simply hanging, mechanically harmless but being charged with electricity any
person coming into contact therewith might be killed by the shock or seriously
damaged.
The object of this invention is to prevent accidents from the latter cause, and
for this purpose I divide the exposed overhead conductor, or trolley wire, into
convenient sections insulated from each other, and each separately supplied with
energy from the main supply cable through a magnetic switch operated by a
shunt current taken from the further end of the section of the exposed overhead
trolley wire, and so connected that whilst the circuit is complete the shunt cur-
rent operates the switch and maintains contact between the supply cable and
trolley wire, but if the trolley wire breaks, the shunt circuit is also broken and
the solenoid or armature of the magnetic switch is released and falls, and contact
trolley wire is broken, and the fallen or hanging
between the main supply cable
wire is no longer electrically dangerous.
When the current has been once broken the arrangement of the switch is
preferably such that current can only be restored by temporary connection with
the preceding section, and this can conveniently be done by so arranging the
trolley that it will span two sections. A small hand switch may be placed in
the box for this purpose.
The box containing the switch may also be fitted with an automatic cut out
or fuse so that in the event of a short circuit occurring in any part of the line
only that portion where the short circuit occurs is cut out, instead of the whole
system as is the case where the cut outs are at the generating station. Also as
the fuse or cut out can be set to the maximum current required only on a
section instead of on the whole line, the strain upon the dynamos and engines
at the generating station are materially reduced.
T # Tune 1899.
STALDOVD SWITH.
COMPLETE DI
Improved Means of Lessening the Danger.Attendant upon the
Employment of Overhead Conductors. in Electric Tramways.
I, MICHAEL HOLROYD SMITH, of Albany Buildings, 47, Victoria Street, West-
0minster, Consulting Engineer, do hereby declare the nature of this invention and

page_text: in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
The use of overhead conductors for electric tramways presents two dangers
to the public, one mechanical, one electrical, for in one case the overhead wires
might so break that the swish of the falling wire, suddenly relieved from tension,
would kill or seriously damage any living creature it might strike. In the other
case a wire might break and in its fall do no damage or simply be left hanging
mechanically harmless, but being charged with electric energy any person coming
into contact therewith might be killed by the shock or suffer serious damage. The
object of this invention is to prevent accidents from the latter cause.
In order that this invention may be more easily understood, reference is made
to the accompanying drawings in which Fig. 1 is a diagramatic view of a section
of an electric tram-line, and Fig. 2 a detail of showing an attachment for the
trolley wires. For the purpose of this invention the overhead conductor or trolley
wire T is divided into sections of suitable length, the chief point to consider in
determining the length of these sections being the frequency of this car service,
and the amount of street traffic. The sections are insulated from each other
as shown at A A Fig. I and in greater detail Fig. II.
Each section is separately supplied with electric energy from the main under-
ground insulated supply cable B, through a magnetic switch, a method of doing
so is shown diagramatically at C and C Fig. I where it will be seen that a
wire DD connects the main cable to the terminal E, within the box C. From
the terminal D a shunt wire passes round the magnet M to the terminal F
thence through a fuse to the terminal G from which an insulated wire H, of
sufficient capacity to supply a section, is taken to the insulated stud I & electrically
connected to the trolley wire. From the other end of the section a fine wire K
is passed to the rheostat R within the supply box and from the rheostat con-
nection is made with the rail S completing the return circuit to the generating
station. The current passing round the wires of the magnet M energizes it and
causes it to attract the armature L, which is provided with an arm for closing
the connection between the terminals E and F thus making connection by means
of the fuse & the terminal G between the supply cable and the section of trolley
wire. It will be seen that the current for the cars on the section is also passed
round the magnet M. Should a section of the trolley wire break in any portion
of its length then the current flowing round the magnet M would cease and the
spring N would draw off the armature L breaking the connection between the
terminals E & F. and thus freeing the trolley wire from electric connection with
the supply cable B.
As previously stated Fig. I is diagramatic, the switch boxes in practice could
be in the base of the poles, or in a box on the footpath or in an adjacent
house as might be most convenient. The arrangement of switches, magnets,
resistances and wiring are also capable of many modifications and I do not con-
fine myself to the precise arrangement shown.
Fig. 2 shows in detail a construction of a junction of two sections that could
be conveniently put into practice, and it is designed to withstand the strains
that would come upon the standing sections, right and left, of the broken section,
and for this purpose a bar or plate P is supported by the span wire or cross
arm from the pole and carries by duplicate insulators on either side the
studs holding the trolley wire. One of these studs X at the commencement of a
section is extended through the insulator and forms a terminal for connecting
the supply wire H. Whilst the stud X at the other end of the section forms a
terminal for the shunt wire K.
When a section of trolley wire is broken and the connection interrupted it is
not intended that it should be restored except by opening the box, but should a
temporary interruption occur, it may be restored by a trolley passing from one
section to the other and spanning the gap.

page_text: A secondary use of the arrangement described is, that in the event of a shore
circuit securing the fuse in the box, set for the demand of a section only, would
act, thus localizing a fault, and materially lessening the strain upon the entire
are arranged at the generating station,
plant which occurs when the "cut-outs
because it is then necessary to set them to the full demand of the line.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to to be performed, I declare that what
I claim is:-
1. In electric tramways with overhead conductors dividing the trolley wire
into sections separately connected with the supply cable in such a manner that
should the trolley wire break its electric connection with the supply cable shall
be immediately interrupted in a manner substantially as herein described.
2. In electric tramways with overhead conductors the combination of sections
of trolley wires with electro magnetic switches, rheostats, fuses and connections
substantially as and for the purpose described.
3. In electric tramways with overhead conductors connecting different sections
of the trolley wire substantially as and for the purpose described and illustrated
in Fig. 2.