Improvements in and relating to the Electrical Propulsion of Tramway Cars, Railway Carriages, and the like, by a Road Contact System.
Year: 1898

page_text: Date of Application, 10th Nov., 1898
Complete Specification Left, 9th Aug., 1899-Accepted, 23rd Sept., 1899
PROVISIONAL SPECIFICATION.
Improvements in and relating to the Electrical Propulsion of
Tramway Cars, Railway Carriages, and the like, by a Road
Contact System.
J. "F
I, DAVID ROBERTSON, Junior, of Glendale, Uddingston, in the County of
Lanark, Electrician, do hereby declare the nature of my invention to be as
follows:
This invention has reference to and comprises improvements in and relating
to the electrical propulsion of tramway cars, railway carriages, and the like,
and consists of an improved method of and devices for transmitting electric
current from underground conductors to the motors of such vehicles by means
of contact studs placed between the rails, very slightly above the street level,
and sliders or skates attached to the vehicles.
In carrying into practice the improvements of this invention, besides the
main circuit conveying electricity to drive the motors, an auxiliary circuit is
used, fed by a small auxiliary dynamo working at a low pressure say about
25 volts, and this auxiliary current is used to actuate automatic switches and
make electric connection between the main circuit and the motors as the sliders
of the cars pass over the contact studs, in the manner to be described, the
switches being arranged so that each main contact is alive only when the car
is over it.
'
In addition to the main contacts, which are laid along the center of the track,
there are other two sets of contact studs in line on one side of the centre one
set of these being placed alongside the main contacts and the other midway
between them.
66
"
The former set are connected to the coils for working the corresponding
switches and are herein called the "switch contacts," while the latter set called
auxiliary contacts are joined permanently to the auxiliary circuit. Besides
the main skate each car has a second skate, or slider, which makes contact with
these studs, and serves to connect the switch studs to the auxiliary circuit.
Whenever this takes place, a current is passed through the coil of the auto-
matic switch which is put on and the main slider can pick up current from the
corresponding main contact.
As soon as the auxiliary slider leaves the switch contact the automatic switch
is released, and the corresponding main contact is disconnected from the high
pressure mains.
The car is thus always ready to pick up current, and no storage batteries
are required, while at the same time the live contacts on the main circuit are
always covered by the car.
The auxiliary studs are always live, but as they are at a very low pressure
this cannot cause any danger or inconvenience.

page_text: It is also quite impossible for the ordinary street traffic to work the switches,
since this can only be done by putting two studs 10 to 20 feet apart into direct
metallic connection. Where necessary the switch contacts can be shielded
from leakage of the main current by surrounding them by a metal ring or box
connected to the rails, which form the return for both the main and auxiliary
circuits.
The pitch of the main contacts will be a little less than the length of the
shortest car intended to be run on the route, and the switches can either be
placed below their studs or for convenience and economy grouped together in
manholes.
It is not necessary to place the main slider and contacts in the centre but in
most cases it will be found preferable to do so, and to put an auxiliary slider on
each side of the main slider, so that the switch and auxiliary contacts may be
placed on either side of the centre. This facilitates turning sharp curves, where
it is best to have the auxiliary studs on the inner side of the curve.
In long lines the auxiliary circuit may with advantage be fed at a few points
by a motor generator driven from the main circuit.
The automatic switch consists essentially of a piece of iron (conveniently a
tube) which floats in mercury but can be pulled down by a current in a sur-
rounding coil of wire in the manner of a solenoid. When the iron goes down
the mercury rises by displacement and makes contact with a metal rod pro-
jecting downwards from the insulating cover.
Current from the main circuit then enters by the terminal at the top, through
the metal rod and mercury to the metal case of the switch whence it is led by a
cable to the proper stud, thence through the slider to the motor which is con-
nected therewith.
The whole is supported on an insulator and the necessary connection at the
top is conveniently made by a fuse to a bus bar supplying all the switches in
one manhole.
A thick tube of insulating material is fixed to the inside of the moving iron
tube to make it float higher out of the mercury and also to prevent the possibility
of an arc between it and the metal rod.
The central rod of iron projecting from the bottom is principally to save mer-
cury but also to assist the magnetic effect and reduce the electric resistance.
In order to save wear at the switches the auxiliary skates are made longer
than the main one so that the current is always broken at the surface contacts
and the switch never has to stop a current in ordinary working.
The sliders may be attached to the cars by springs and may especially for
long cars be made in several sections jointed together.
Dated the 9th day of November 1898.
W. R. M. THOMSON & Co.,
96, Buchanan Street, Glasgow, Agents.
Improvements in and relating to the Electrical Propulsion of
Tramway Cars, Railway Carriages, and the like, by a Road 4
Contact System.
I, DAVID ROBERTSON, Junior, of Glendale, Uddingston, in the County of
Lanark, Electrician, do hereby declare the nature of my invention and in what
manner the same is to be performed, to be particularly described and ascertained

page_text: in and by the following statement in writing reference being made to the
accompanying drawings:-
°
This invention has reference to and comprises improvements in and relating
to the electrical propulsion of tramway cars, railway carriages, and the like,
and consists of an improved method of and devices for transmitting electric
current from underground conductors to the motors of such vehicles by means
of contact studs placed between the rails, very slightly above the street level,
and sliders or skates attached to the vehicles. And in order that my said in-
vention may be properly understood I have hereunto appended one sheet of
explanatory drawings in which Figure 1 is a diagram illustrating one arrange-
ment for transmitting electric current and Figure 2 is a plan of part of a tram-
way line, while Figures 3 and 4 are respectively a sectional elevation and a plan
partly in section of my new or improved switch.
Referring to these drawings:-
In carrying into practice the improvements of this invention as indicated in
Figures 1 and 2 besides the main circuit A conveying electricity from the
generator B to drive the motors C, an auxiliary circuit 1 is or may be used,
fed by a small auxiliary dynamo E working at a low pressure say about 25
volts, and this auxiliary current is used to actuate automatic switches F and
make electric connection between the main circuit A and the motors C as the
sliders G, H, of the cars pass over the contact studs, G1, G2, H, in the manner
to be described, the switches being arranged so that each main contact is alive
only when the car is over it.
In addition to the main contact studs H', which are laid along the centre of
the track, there are other two sets of contact studs G1, G2, in line on one side
of the centre, one set G¹, of these being placed alongside the main contacts H',
and the other G2, midway between them.
"
The former set G¹ are connected to the coils for working the corresponding
switches F, and are herein called the "switch contacts," while the latter set G²,
called "auxiliary contacts are joined permanently to the auxiliary circuit D.
Besides the main collecting skate H each car has a second skate, or slider G,
which makes contact with these studs, and serves to connect the switch studs G¹,
to the auxiliary circuit I), through the stud G².
Whenever this takes place, a current is passed through the coil of the auto-
matic switch F, which is put on and the main slider H can pick up current
from the corresponding main contact stud H¹.
As soon as the auxiliary slider G, leaves the switch contact G', the automatic
switch is released, and the corresponding main contact H', is disconnected
from the high pressure mains A.
The car is thus always ready to pick up current, and no storage batteries are
required, while at the same time the live contacts on the main circuit are always
covered by the car.
The auxiliary studs are always live, but as they are at a very low pressure this
cannot cause any danger or inconvenience.
It is also quite impossible for the ordinary street traffic to work the switches,
since this can be only done by putting two studs 10 to 20 feet apart into direct
metallic connection. Where necessary the switch contacts can be shielded
from leakage of the main current by surrounding them by a metal ring or box
connected to the rails, which form the return for both the main and auxiliary
circuits.
The pitch of or distance between the main contacts H¹, will be a little less
than the length of the shortest car intended to be run on the route, and the
switches can either be placed below their studs or for convenience and economy
grouped together in manholes as indicated in Figure 2 at R.
It is not necessary to place the main slider and contacts in the centre but in
most cases it will be found preferable to do so, and to put an auxiliary slider on

page_text: each side of the main slider,. so that the switch and auxiliary contacts may be
placed on either side of the centre. This facilitates turning sharp curves, where
it is best to have the auxiliary studs on the inner side of the curve.
In long lines the auxiliary circuit may with advantage be fed at a few points
by a motor generator driven from the main circuit. Otherwise however the
current to operate the switches may be drawn from the main circuit or be sup-
plied by a battery or other source carried on the car.
The automatic switch as shown in Figures 3 and 4 consists essentially of a
piece of iron I, (conveniently a tube) which floats in mercury J, but can be
pulled down by a current in a surrounding coil of wire K, in the manner of a
solenoid. The mercury and tube being contained within a tube S of glass or
other insulating material. When the iron goes down the mercury rises by
displacement and makes contact with a metal rod L projecting downwards
from the insulating cover M.
Current from the main circuit then enters by the terminal N, at the top,
passes through the metal rod L, and mercury J, to the terminal O, whence it is
led by a cable O¹, to the proper stud, thence through the slider H, to the motor C
which is connected therewith.
Otherwise in a converse and analogous manner, the moving part may be a
solid rod and the electric connection made through a tube surrounding it con-
nected to the upper terminal and carried by the insulating cover.
The whole may be bolted to a shelf in the manhole which is connected to the
rails to form the return for the coil, the inner end of which is preferably soldered
to the case and the necessary connection at the top is conveniently made by a
fuse to a bus bar supplying all the switches in the one manhole.
A thick tube P of insulating material is fixed to the inside of the moving
iron tube I, to make it float higher out of the mercury and also to prevent the
possibility of an are between it and the metal rod L.
The object of the central rod of iron Q projecting from the bottom is prin-
cipally to save mercury but also to assist the magnetic effect and reduce the
electric resistance.
In order to save wear at the switches the auxiliary skates are preferably made
longer than the main one so that the current is always broken at the surface con-
tacts and the switch never has to stop a current in ordinary working.
The sliders may be attached to the cars by springs and may especially for long
cars be made in several sections jointed together.
Having now particularly described and ascertained the nature of my said in-
vention and in what manner the same is to be performed I declare that what I
claim is:
First. In a stud contact system for the electrical propulsion of tramway cars,
railway carriages, and the like, the combination with a main circuit for supply-
ing current to the motors through automatic switches, contact studs and a
collecting skate on the car, of an improved auxiliary circuit conveying current
from an independent generator for the operation of the automatic switches
through branches, contact studs and a collecting skate on the car, in which
circuit the return is through the rail to which the coils of the switches are
electrically connected, substantially as herein described and illustrated by the
accompanying drawings..
Second. In a stud contact system for the electrical propulsion of tramway
cars, railway carriages and the like, the combination with collecting skates
carried on the vehicle, and road contact studs connected to the main driving
circuit and to an auxiliary circuit, of an automatic switch constructed substan-
tially as herein described and illustrated by Figures 3. to 4 of the accompanying
drawings.
Third. In a stud contact system for the electrical propulsion of tramway cars,
'railway carriages and the like the combination with collecting skates carried

page_text: on the vehicle and road contact studs connected to the main driving circuit of
an automatic switch constructed substantially as herein described and illustrated
by Figures 3 and 4 of the accompanying drawings.
Fourth. Automatic switches for use in combination with a road contact
system of electrical propulsion of tramway cars, railway carriages and the like
constructed substantially as herein described and illustrated by Figures 3 and 4
of the accompanying drawings.
Fifth. In automatic switches of the class described the combination with a
coil of an iron tube or rod within the coil and floating in mercury which is cap-
able of being raised by the drawing down of the tube or rod to make contact
between a rod or a tube depending from the insulating cover and a rod pro-
jecting up from the lower terminal within the mercury, substantially as herein
described and illustrated by Figures 3 and 4 of the accompanying drawings.
Dated the 8th Juaust 1000
W. R. M. THOMSON & Co.,
96, Buchanan Street, Glasgow, Agents.
W. R. M. THOMSON & Co.,
96, Buchanan Street, Glasgow, Agents.