Improvements in Electric Traction on a Road Contact or like System.
Year: 1899

page_text: Date of Application, 4th July, 1899
Complete Specification Left, 3rd May, 1900-Accepted, 4th July, 1900
PROVISIONAL SPECIFICATION.
Improvements in Electric Traction on a Road Contact or like System.
We, SILVANUS PHILLIPS THOMPSON, of Morland, Chislett Road, West Hamp-
atead, Doctor of Science, and MILES WALKER, of St. John's College, Cambridge,
Engineer, do hereby declare the nature of this invention to be as follows:-
Our improvements are directed in the first place to make more practicable
those systems of electric traction in which a magnet on the car is used to operate a
switch and connect a road-stud to the supply main.
When the frame of the car permits, we prefer to use two or more skates
arranged in tandem, some of which make contact with a stud when it is at a
high potential and some of which make contact with it when it is connected to
a low potential main. In this case we need not have the magnet extending to the
same length as the skate because safety is secured by the complete earthing of
the studs. It is sufficient to have a magnet to close a switch connecting a stud
to the high potential main and another magnet which subsequently comes into
operation which opens the switch and puts the same stud in connection with the
low potential main. The same switch can be made to alternately open and
close (upon receiving similar impulses from the magnets) by using a rocking
lever whose centre of gravity is above the pivot and by lifting the rocking lever
to the point of unstable equilibrium. by means of the magnet, there being a
bias tending to make the lever fall to the side opposite to that on which it was
before being lifted.
Another method is to make the armature of the switch move in a path parallel
or nearly parallel to the surface of the road and move it by means of a long
magnetic pole on the car, whose line is inclined to the direction of the rails.
Thus by inclining the magnet pole to one side or the other the switch can be
closed or opened.
It is for some purposes advantageous to design the stud so that it can rise above
the level of the road and when this is done we obviate, in the following manner,
the difficulties which have hitherto arisen from the friction of the moving parts
The moving stud instead of being a peg sliding in vertical supports consists of
a lever turning about a pivot placed underground. The hole in the roadway
through which the shank of the stud moves is made much larger than the cross-
section of the shank and is ordinarily closed by the enlarged head of the stud,
thus no friction can occur on account of the side pressure of the skate except on
the said pivot which is well sheltered from water and mud from the street. The
opening through which the shank works has an inwardly turned lip which conducts
all mud and water away from the meclianism of the switch. A stud of this kind
has so little friction that it can be easily raised by a magnet carried on the car.
The part of the magnet which comes in contact with it and raises it may consist
of an inclined plane of iron the point of which dips down when it comes to a
stud by reason of its magnetic attraction, or it may consist of a pivotted piece
ordinarily hanging clear of the roadway (or just touching it) which after becoming
attached to the stud turns on its pivot and raises it, at the same time breaking the
E

page_text: exciting current. The enlarged head of the stud is designed to protect the insula-
tion of the shank so that when the stud is raised no current can leak from it.
The pivot of the stud is carried through a water-tight joint and a lever
attached
to it which operates the switch contacts. But we sometimes combine rising
studs with electromagnetic switches such as are well known in the art, and con-
nect the studs with the moving parts of the switches so that they can be raised
and lowered thereby. We also combine studs of this kind with a mechanical
means of depressing them, such as an inclined plane carried on the car.
Improvements in Electric Traction on a Road Contact or like System.
We, SILVANUS PHILLIPS THOMPSON, of Morland, Chislett Road, West Hamp-
stead, London, Doctor of Science, and MILES WALKER, of St. John's College, Cam-
bridge, 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:—
Our improvements relate to surface contact systems of electric traction in
which a magnet on the car is used to operate a switch and connect a road stud
to the supply main.
When the frame of the car permits we prefer to use two or more skates
arranged in tandem, some of which make contact with a stud when it is at a
high potential and some of which make contact with it when it is connected to
a low potential main. In this case we use a magnet to close a switch connecting
a stud to the high potential main and another magnet to open the switch sub-
sequently and put the stud in connection with the low potential main.
It is for some purposes advantageous to design the stud so that it can rise above
the level of the road and when this is done in order to minimise the friction of
the moving parts the stud is made in the form of a lever turning about a pivot
placed underground. We may attach a lever to the stud lever to operate the
switch contacts. The rising studs may, however, be combined with electro-
magnetic switches, such as are well known in the art and be connected electrically
with the moving parts of the switches so that the switches can be raised and
lowered thereby.
.
We will now proceed to describe our improvements with reference to the accom-
panying drawings, in which
Figure 1 illustrates a switch adapted to be operated first by one magnet and
then by another carried by the car in order to place a stud first in connection
with the high potential main and subsequently in connection with the low
potential main.
Figure 1 is a side elevation of part of the mechanism shewn in Figure 1.
Figure 2 shews a diagram of the connections for a surface contact system in
which two or more skates are arranged in tandem, one of which makes contact
with a stud, when connected to a high potential main, while the other makes
contact with it when connected to a low potential main. Two magnets are pro-
vided to operate a switch of the kind shewn in Figure 1.
Figure shews a pivoted rising stud in its box, partly in section and partly
in elevation.
Figure 4 is a plan of the same.

page_text: Figures 5 and 6 shew similar views of a stud which itself operates a switch
whereby it connects itself to the feeder main.
Figure 7 shews diagrammatically the method of working in which the rising.
stud is electrically connected to a separate electromagnetic switch so that the
rising or falling of the stud causes the switch to close or .open.
In Figure 1, the stud 1, which is preferably of iron, is connected with two
contact blocks 3, 2, respectively adapted to be placed in connection with the
contact blocks 4 and 5 connected respectively to the high potential and low
potential mains. The iron plunger 6 guided in the guide-piece 7 and arranged
vertically under this stud 1, is provided with a rack 8 at its lower end gearing
with a pinion 9 loosely revoluble on the axle 10 supported in bearings 11 (see
Fig. 1). The ratchet wheel 12 is rigidly connected to the pinion 9 and is
adapted to drive the crank discs, 13. 13, through the spring pawl 14 pivoted on
one of said crank discs. A connecting rod 15 is driven from the crank pin 16
and operates the switch lever 17 through the arm 18. When the plunger G
is at its lowest position, as shewn in Figure 1, the switch arm; 18 is at its
extreme left position, in which position the stud 1 is connected through contact
blocks 2 and 5 and the switch lever 17 to the low potential main. The distance
through which the plunger rises each time on being attracted by the magnets on
the car is such that it moves the pinion 9 through 180° each time that it rises
so that when the plunger is in its uppermost position the arm 18 is carried to
its extreme right position and the switch lever connects the contact block 3 with
the contact block 4 connecting the stud 1 with the high potential main. After
the magnet which has raised the plunger 6 has passed on, the plunger drops and
rotates the pinion 9 and ratchet wheel 12, backwards, the pawl 14 sliding over
the teeth of the ratchet wheel. To ensure the crank discs 13 remaining stationary
during the downward movement of the plunger a detent 19 is provided to engage
with a toothed wheel 20 rigidly connected with said crank discs. We may
equivalently replace the sliding piece or plunger 6 by a pivoted piece in which
case we gear said piece to the pinion by means of a segment of a toothed wheel,
also so arranged that every time the piece is attracted by a passing magnet, the
pinion is turned forward through 180°.
The function of the mechanism illustrated in Figure 1 will be the better
understood by reference to Figure 2 which shews said mechanism in its four
positions. S₁ 8, so are six studs under which are arranged six switches of
the type shewn in Figure 1. The high potential feeder main 21 is electrically
connected with the switch contact blocks 4. 4, and the low potential feeder main 22
is electrically connected with the switch blocks 5, 5: The direction of the motion
of the car carrying the magnets 23 and 24 and the tandem skates 25 and 26 and
motor 27 is shewn by the arrow.
In the normal position each switch connects its stud to the low potential main
through contacts 2, 5, as shewn in the case of the stud s,. When the leading
magnt 23 reaches a stud it lifts the plunger 6 and operates the switch connecting
the stud to the high potential main through the contacts 3, 4, as shewn at 5..
When the magnet 23 passes on from a stud the plunger drops leaving the stud
connected to the high potential main, so that when the skate 25 passes on to the
stud current is supplied to the motor through said skate from the high potential
main, as shewn at Sa When the skate 25 passes away from a stud and the
second magnet 24 passes over it, said magnet lifts the plunger 6 operating the
switch and connecting the stud to the low potential feeder main as shewn at sa
Subsequently the magnet 24 passes away from the stud leaving it so connected
that it can take the return current from the skate 26 (as shewn at s), the stud
then being in its normal position ready for being operated again when the next
car reaches it.
In cases where it is for some purposes advantageous to design the stud so that
it can rise above the level of the road we obviate the difficulties which have
hitherto arisen from the friction of the moving parts in the following manner:-

page_text: The moving stud instead of being a peg sliding in vertical supports consists
of a lever turning about a pivot placed underground, as shewn in Figures 3, 4, 5,
6 and 7. In Figures 3 and 4, 27 is the head of the stud, and 28 the shank,
the whole being pivoted at 29 in the block 30 which is fixed by means of insulated
screws 31, 31, to the lid of the box from which said block is insulated by the
trough 32. The shank 28 is flattened out as shewn to reduce the magnetic
reluctance and this wider portion moves between the two iron pieces 33, 34 which
are part of the cast iron box 25. The upper portion 36 of the box and lid 37
are made of gun-metal or other suitable non-magnetic material; the hole in the
lid terminates in a lip 38 which is adapted to lead any wet and mud away from
the moving parts. The whole surfaces of the shank 28. and the block 30 are
thoroughly coated with a suitable insulator, as are also the heads of the screws 31,
31. The stud shewn in Figures 3 and 4 is arranged for working with a separate
switch which connects it with the feeder main when required. Figures and 6
shew a similar stud which itself operates a switch, thus connecting itself in circuit
with the feeder main parts corresponding to the parts of the stud shewn in
Figures 3 and 4 are lettered as before. The stud lever or shank. 28 is rigidly
fixed to the spindle 39 to which is also keyed or otherwise fixed a lever 40 the
spindle passing through water-tight glands into the box.41. Said box is pro-
vided with a removable cover 42 which has been removed in Figure 4 to shew
the switch in the interior of the box.
1.
When the stud rises the arm 40 comes into contact with the insulated terminal 43
which is connected to the feeder main through a mercury cup contact 44. The
dotted lines 45 shew the stud in its raised position in contact with the magnet 46,
also shewn dotted. It is thus clear that when the magnet 46 reaches a stud it
raises the same and closes the contact between 40 and 43, thus connecting the
stud directly to the feeder main.
In Figure 7 we shew a method of working in which the rising of a stud operates
a switch electrically to connect the stud with the feeder main. The falling of
the stud opens the switch and disconnects the stud from the feeder main. The
arm 47 which is similar to the arm 40, Figure 5, is rigidly attached to the stud
shank or lever 28, but the arm 47 may be made much smaller than the arm 40.
When the stud rises owing to the attraction of the magnet 49 carried by the car,
said magnet being at a higher electric potential than the earth, by being con-
nected through another stud to the high potential main; the arm 47 makes contact
with a contact block 48 connected to one end of a high resistance switch wind-
ing 50, the other end of which is connected to earth, or to the return conductor.
The switch magnet thus becomes energised and the switch is closed connecting
the stud through the switch contact blocks 51, 52, 53, 54 to the high potential
feeder main 55, the connection to the stud in the box being made in the way
shewn in Figure 3.
'
The general outline of the magnet 49 is shewn in Figure 7, the ends being
lower than the middle portion and connected therewith by inclined planes. The
lower portions however do not touch the studs until these have risen some
distance.
The method of operation is as follows:-
The magnet 49 which is in contact with the high potential main 55 through
the stud raises the studs, which gradually rises up the incline of the magnet
until the arm 47 makes contact with the block 48 when the switch winding 50
is energised and the switch 56 is closed, connecting the studs, to the high
potential feeder main. Current is then supplied through this stud to the car
until the other end of the magnet reaches it when it is depressed and the contact
between the arm 47 and contact block 48 is broken; as shewn at whereby current
is cut off from the coils of the main switch which thereupon opens. The stud s
has however come into operation before the studs, is disconnected from the high.
potential feeder main.

page_text: 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 two tandem
skates with two magnets carried by a car arranged to operate upon the same studs.
the one magnet operating switches to connect the studs with a high potential' feeder
main and the other magnet subsequently operating the same switches to connect
the studs with the lower potential main, substantially as described.
2. In a surface contact electric traction system, a stud normally connected to
earth, and adapted on being operated by a magnet on the car to rise above the
level of the road, consisting of a lever pivoted underground on an insulated block
so that on rising said stud is insulated from earth, substantially as described.
3. In a surface contact electric traction system, the arrangement of a rising
stud which on being operated by a magnet on the car becomes electrically con-
nected with, and conducts current to, the circuit of an electromagnetic switch,
whereby said electromagnetic switch is closed (or raised) and opened (or lowered)
by said stud' to respectively connect and disconnect said stud with or from the high
potential main, substantially as described.
4. The systems of electric traction with surface contacts arranged and operated
substantially as described with reference to Figures 1; 1, 2 and 7 of the accom-
panying drawings.
Dated the 3rd day of May 1900!
W. P. THOMPSON & Co.,
322, High Holborn, London, WC.,
Patent Agents for the Applicant.