Year: 1899

page_text: We, SILVANUS PHILLIPS THOMPSON, of Morland, Chislett Road, West Hamp-
stead, London, Doctor of Science, and MILES WALKER, of St. John's College,
Cambridge, Electrical Engineer, do hereby declare the nature of this invention
to be as follows:.
Our invention relates to those systems of electric traction in which the electric
current is supplied to the cars or locomotives from studs or sections of rail each
of such studs or sections of rail being in turn connected to a main conductor by
means of an automatic switch when the car is above or near it and disconnected
from the main conductor after the car has passed on.
In order that no stud shall be ever left connected to the high pressure main
after the car has passed it, and for other reasons which appear below, we arrange
the automatic switches so that a stud is first connected to the high pressure main
and supplies current to the car and is then connected to the low pressure main
or earthed rail and takes the current leaving the car. Each stud under these
circumstances must of necessity be connected to the low pressure main before
the car leaves it; for if it were not so connected current could not flow through the
car circuit. For this purpose it is convenient to employ two or more skates on the
car one or some of which makes or make contact with a stud when it is at high
potential and the other or others of which makes or make contact with it when it
is at low potential. The automatic switches may be operated either by shunt
wound magnets or series wound magnets or by both. We find it convenient to
use a shunt magnet to operate the switch and a series magnet to
keep the switch closed and it is advisable in this case to make the
shunt magnet break its own circuit after the switch is closed. It is
better to connect a series coil between the stud and the low potential main
or earth than between the high potential main and stud. One way of arranging
the studs is to inter-connect all the alternate studs say Nos. 1, 3, 5 &c. into one
system such that the switch which connects one of them say No. 3 to the high
potential main connects one other or some others of them say No. 1 & 5 to the low
potential main. The other alternate numbers say Nos. 2, 4, 6, &c. form another
system. This method greatly facilitates the connecting up of the above mentioned
series coils because of such coils are placed between the switch and the low
potential main they are fed by current coming from the switch whatever stud
such current may have come from. Thus the multiplication of series coils is
obviated.
When shunt coils are used to actuate the switch we use one or other of the
following methods. of making the shunt coil inoperative at the time when the
switch should open. The shunt coil whose terminals we will call A, B may be
joined permanently or temporarily in series with a resistance whose terminals
"we will denote by B, C. When A is joined to the positive main and C to the

page_text: Many
negative main the shunt coil is in operation. When we wish to throw the coil
out of operation we join B to the positive main thus short circuiting A. B. A
simple way of doing this is to have B connected to a road-stud with which a
skate on the car makes contact. The resistance B C may conveniently constitute
the winding of an electromagnet whose action facilitates the opening of the switch.
Another method of putting a shunt coil out of action is to break its current or
short circuit it by means of a mechanical device pressed down by the car.
such mechanical devices have been suggested for actuating switches and though
there are several objections to their use for this purpose those objections do not
apply with equal force to a device which merely has for its function the cutting
out or short circuiting of a shunt coil. Yet another method can be employed.
A magnet on the car can be made to attract an armature under the road and that
armature by its movement may be made to break the shunt coil circuit or to short
circuit it.
Our invention also relates to a method of fixing and insulating the studs. The
stud consists of a mass of metal embedded in stone and has a wearing cap fixed
in a bevelled seat capable of being removed by punching out or hammering away
one or more rivets or fixing pegs.
Dated this 24th day of January 1899
SILVANUS PHILLIPS THOMPSON,
MILES WALKER.
We, SILVANUS PHILLIPS THOMPSON, F.R.S., Doctor of Science, of "Morland,"
Chislett Road, in the County of London, and MILES WALKER, Electrical Engineer,
of St. John's College, Cambridge, 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:-
Our invention relates to those systems of electric traction in which the electric
current is supplied to the cars or locomotives from studs or sections of rail in the
road, each of which studs or sections of rail is in turn connected to a main or
high pressure conductor by means of an automatic switch when the car is
above or near it and disconnected from the high pressure conductor after the
car has passed on.
In order to prevent any stud from remaining connected to the high pressure
main after the car has passed it and for other reasons which appear below, we
arrange the automatic switches so that a stud is first connected to the high pressure
main and supplies current to the car and is then connected to the low pressure
main or earthed rail and takes the current leaving the car. Each stud under
these circumstances must of necessity be connected to the low pressure main
before the car leaves it, for if it were not so connected current could not flow
through the car circuit and moreover the low pressure skate comes in contact with
each stud before the car leaves it.
For this purpose it is convenient to employ two or more skates on the car
one or some of which makes or make contact with a stud when it is at high
potential and the other or others of which makes or make contact with it when
it is at low potential.
In the accompanying drawings:
Figure 1 is a diagram illustrating an electric traction system arranged accord-
ing to our invention.

page_text: Figures 2 and 3 are diagrams shewing modifications and
Figure 4 is a diagram of a modified form of switch.
Figure 5 is a vertical section of an improved stud or road contact constructed
according to our invention.
The most general arrangement is shewn in Figure 1, where S, S represents a
single row of studs over which the skates K' and K pass successively the ordinary
direction of motion of the car being indicated by the arrow. The contact bar Y
of the switch may be operated by a magnet on the car, by electromagnetic means,
by mechanical means or by any other suitable method of operating automatic
switches. When the high potential skate K' is in contact with S, the yoke piece Y
makes contact between the high potential main F¹ and the stud as shewn in
switch No. 2 (Figure 1). The current then passes from K¹ through the motor M
to K3 which is in contact with the stud of switch No. 4 that stud being at that
time connected to the low potential main F2 which may in some cases be the rail
Litself. Between-switch-No.-2-and-switch-No.-4-is-switch-No.--which-changes-
the connection of its stud in the interval of time which elapses between its contact
with B, and contact with K². The yoke Y may be made to fall naturally into
the position shewn in switch No. 4 or it may be made to normally take up an
intermediate position as shewn in No. and be only moved to the position shewn
in No. 4 by a magnet on the car or by other well known means. In this latter case
the studs are not connected to either main when the car is not near them. The
main feature of the invention is that the low potential skate K2 (upon the
good working of which the running of the car is dependent) must necessarily come
in contact with each stud after it has been made alive and subsequently discon-
nected, thus forming an absolute check upon the safe working of the system.
Another great advantage gained is that it is possible to run the car without an
earth return and yet only use one row of studs. When electromagnetic switches
with series coils are used one way of inter-connecting is, shewn in Figure 2. In
the position there shewn the current is coming from the main F¹, passing through
switch No. 2 to the skate K¹ thence through the motor M to skate K2 thence
through switch No. 4 to the magnetising coil m of switch No. 2 and thence to the
return feeder Fa.
When the car moves on in the direction indicated by the arrow the stud $
of the electromagnetic switch No. 1 will not be connected with the high potential
main F until part of the return current from the motor passes from the skate K³
to the stud S of the switch 3 and through the actuating coil m of the switch 1,
whereby, the contact bar Y of said switch will be caused to make contact with the
main F. Hence it will be impossible to operate the switch No. 1 unless the
contact bar Y of switch No. 3 is in the position shewn, that is, disconnected from
the main F. It will be evident without further description that in this system
the studs bearing odd numbers are operated independently of the even numbers,
but the studs are inter-connected SO that the passage of current to
an even number connected to one main holds the next even number
before or behind in connection with a main of opposite polarity, and similarly
the passage of current to an odd number connected to one main holds the next
odd number before or behind in connection with a main of opposite polarity.
One method of employing a shunt coil to operate the switches is shewn in
Figure 3. Here the shunt circuit is carried through a small auxiliary switch R
which can be operated by a magnet on the car. Normally the relay is closed so
that a skate at high potential such as K¹ sends current through the shunt coil and
operates the switch thereby connecting the stud with the main F¹. As the car
passes on K leaves the stud of No. 2 and the magnet G comes over it. This
operates the little auxiliary switch R and breaks the shunt circuit causing the
switch to open. Another method is that shewn in Figure 4. Here the shunt
coil m is placed in series with a resistance W and a point between them is connected
to a subsidiary stud Z. While the switch is in action the stud Z is not connected
to anything else but when it is required to open the switch a subsidiary skate K³

page_text: (which is at the same potential as K¹) slides on to Z short circuiting the shunt
coil.
The auxiliary switches may be operated by a magnet on the car in any of the
ways wellknown in the art.
Referring now to Figure 5, I is a block of granite or other hard stone having
a hole I¹ through it of the shape shewn in section in Figure 5. A steel bolt B is
passed through the hole and rivetted or screwed down with great force. Upon
the upper end of the bolt is fixed a removable wearing cap C resting on a bedding
piece and this cap is pinned by a piece of metal which is hammered into a
recess 2. When it is required to remove the cap the piece of metal which
pins it can be hammered through the cap and into the bedding piece out of the
way. The conductor f is inserted into the bottom of the bolt B which is counter-
sunk two or three inches into the granite block leaving a deep hole which can be
filled up with molten insulating material.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is :-
1. In a surface-contact electric traction system the combination of a high
potential skate or current collector and a low potential skate or current collector
placed one behind the other in tandem so as to run upon the same row of studs,
the one skate collecting current from a high potential main and the other return
ing current after it has passed through the motor to the low potential main.
2. In a surface-contact electric traction system a single row of studs (numbered
say 1, 2, 3, 4, etc.,) of which the odd numbers (1, 3, 5 etc.) are operated indepen-
dently of the even numbers (2, 4, 6 etc.) but inter-connected substantially as
described so that the passage of current to an even number (4) connected to
one main holds the next even number before (6) or behind (2) in connection with
a main of opposite polarity and interconnected as to the odd numbers in like
manner.
3. An automatic main switch operated by a shunt coil in combination with a
small auxiliary switch in the shunt circuit which auxiliary switch can be opened
at the right time by a magnet on the car substantially as described.
4. An insulated surface contact constructed of a metal bolt passing through a
block of stone and countersunk substantially as described with reference to
Figure 5.
5. The various systems of electric traction with surface contacts arranged and
operated substantially as described with reference to Figures 1 to 4 of the accom-
panying drawings.
Dated the 25th day of October 1899.
W. P. THOMPSON & Co.
322, High Holborn, London, W.C., Patent Agents for the Applicant.
W. P. THOMPSON & Co.
322, High Holborn, London, W.C., Patent Agents for the Applicant.