Year: 1897

page_text: We, SILVANUS PHILLIPS THOMPSON, of "Morland," Chislett Road, West Hampstead,
in the County of Middlesex, Fellow of the Royal Society, and MILES WALKER, of 23,
Southcote Road, Tufnell Park, in the County of London, Electrical Engineer, do
hereby declare the nature of this invention to be as follows:-
Our invention relates to safeguards for use in those systems of electric traction in
which the cars derive their electric supply from sectional conductors or conducting
studs laid in the roadway which become connected successively to a main conductor
as the car moves over them. The object of our invention is to diminish the risk of
any stud or sectional conductor being left in connection with the main conductor
after the car has passed.
According to our invention we provide an earthing device which connects each stud
to earth during a short interval of time after the instant at which in the ordinary
course of events the switch connecting it to the main conductor should have opened.
If said switch has not opened or if from any other cause the stud remains in connec-
tion with the main or is "alive "after the instant aforesaid then by reason of the
earthing a large current will pass through the stud, and a fuse provided in its main
connecting wire will be blown so that it is no longer connected. In a device of this
kind it is important that the connection to earth should be maintained for a sufficient
length of time to blow the fuse, and therefore a mere trailing brush coming in con-
tact, with a stud is insufficient. On the other hand, it is important that the earthing
should not be maintained for so long a time that the skate or contact shoe of a
closely following car can come in contact with the stud while it is earthed. We
find that we are able to satisfy the proper conditions by having an independent
earthing stud laid in the road ahead of the working stud intended to be earthed and
connected to that working stud through the switch mechanism of the 'working stud
next ahead. Under these circumstances by adjusting the position of the earthing
studs and the length and position of the skate or shoe carried by the car which slides
on and makes contact with the series of earthing studs we are enabled to exactly
fulfil the required conditions. We are able moreover to make this system of earthing
applicable to lines on which the cars run in both directions. We may do this by
connecting the earthing stud over which a car is standing for the time being (through
the mechanism of the switch which for the time being is supplying current to the
car) to the working studs both ahead of and behind the car, both of which studs
should not in the ordinary course of things be " alive."
Sometimes in conjunction with such earthing studs and skate we make a connec-
tion to earth from a working stud which ought at the time to be "dead” through

page_text: the mechanism of a switch box which is the second switch box ahead or the second
switch box behind the working stud so put forth. And sometimes when this second
switch box is employed we are able to dispense with the earthing stud and skate
altogether.
"
we
In order to prevent the current which may leak from the terminal of the switch
which is permanently connected to the main drain from making the stud "alive
surround the insulating material which supports the said terminal with a conducting
band, and connect the said conducting band to enrth.
Dated this 7th day of Angust 1907
We SILVANUS PHILLIPS THOMPSON, of "Morland," Chislett Road, West Hampstead,
in the County of Middlesex, Fellow of the Royal Society, and MILES WALKER, of 23,
Southcote Road, Tufnell Park, in the County of London, Electrical 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 invention relates to safeguards for use in those systems of electric traction in
which electric current is supplied to the cars from surface-contacts such as studs
or sections of rail laid in the road, each of such surface-contacts being in turn con-
nected to a main conductor or feeder main by means of an automatic switch when the
car is above or near said surface-contacts and disconnected from the main conductor
or feeder after the car has passed.
In systems of this kind it is desirable to provide for connecting a surface-contact to
earth after the car has passed the same and at a time when it should normally be dis-
connected from the main so that if by any defect in the switch the surface-contact be
still connected to the main or "alive," a fuse will be blown or some indication of the
defect be communicated to the car. For this purpose it has been heretofore suggested
to employ an auxiliary skate or brush placed at the rear of the car so as to touch the
surface-contact a short time after the main skate has left it, but in practice great
difficulty is experienced in fixing such an auxiliary skate or brush so that it shall
make a reliable contact when the car is going round curves or when it is oscillating
on its springs. This difficulty arises chiefly on account of the great distance that the
auxiliary skate or brush must overhang beyond the car base. Moreover, when the car
is intended to run in both directions complications arise in providing means for
reversing with certainty the said earthing contacts. These difficulties may be to some
extent overcome by mounting the auxiliary skate or brush on separate bogies running
upon the rails, but we propose to entirely avoid these complications by fixing in the
road auxiliary earthing studs, the arrangement and inter-connections of which form
the subject matter of this invention.
Figure 1 is a diagram shewing the arrangement of auxiliary earthing studs
according to our invention for use on a line on which the cars run in one direction
only.
Figure 2 shews the arrangement of our auxiliary earthing studs for use on a line on
which the cars run in both directions and also the method of temporarily connecting
such studs with the main studs.
In Figures 1 and 2, S, S, S indicate the main studs or surface-contacts from which

page_text: the car draws current by means of the main skate K¹. Z, Z, Z are the auxiliary
earthing studs or surface-contacts and K² the auxiliary skate adapted to connect there-
with as the car moves along. The switch contacts C1 and C2, the connections with
the feeder main F F, and the mode of operating the switches are described in the
Specifications, British Letters Patents No. 19455, No. 19455A, and 19456 all dated
1896, granted to us, and need not be further described in the present Specification.
In Figure 1 the car is intended to run in the direction indicated by the arrow. The
stud S of switch No. 1 is permanently connected to an auxiliary stud.Z placed some-
where in advance in switch No. 1. In the figure the auxiliary stud is shown close
beside the main stud of the switch next ahead for convenience in laying the track,
but it may be placed between the two main studs and this course is advisable when a
very long main skate is employed. The auxiliary skate K2 is preferably secured to a
part of the car not very far removed froin the axles of the wheels so that it remains
at the same distance from the rails when the car is going round a curve. The
auxiliary skate it connected to earth E either directly through the car frame, wheels
and rails or indirectly through an electric bell which will give a signal in case the
auxiliary skate should come into action. The distance from the rear end of the main
skate K¹ to the fore end of the auxiliary skate K2 is less by several feet than the
distance between any main stud S and the auxiliary stud Z to which it is connected,
so that it is impossible for K2 to put Z to earth while S is "alive" during the normal
working of the system. If, however, by any accident the stud S remains alive " after
the main skate K¹ has left it, the auxiliary skate K2 coming in contact with Z will
put it to earth and, by causing the feeder fuse to be blown, cut it off from the
source of supply.
A slight modification of the system is necessary, in order to adapt it to lines on
which cars run in either direction; we may for example, fix a second set of auxiliary
studs like Z, Z, Z on the other side of the main studs S, S, S and connect them so
that each main stud is connected to an auxiliary stud both before and behind, or we
may adopt the arrangement shewn in Figure 2, in which the auxiliary stud Z is only
connected to the main studs S, S before and behind when the switch between these
studs is closed. That is to say, when switch No. 2 is closed as shewn in the figure,
stud Z of No. 2 is connected to studs S and S of switches Nos. 1 and 3. The same
arm which operates the switch contacts C¹ and C² also operates the contacts C³, C+
and C, although for the sake of clearness they are shewn in the diagram as being on
opposite sides of the studs. Thus the skate K2 is able to earth the surface-contact
stud of the switch either before or behind.
This plan of cutting off the auxiliary studs by means of the switches has the
advantage of preventing an auxiliary stud which may not be covered by the car from
being made "alive" when the main stud to which it belongs is connected with the
feeder main. It may be employed with advantage in the case shewn in Figure 1
when it is desired to use a skate almost as long as the car.
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
we claim is :-
1. In an electric traction system of the class described, a series of auxiliary studs
each permanently connected to the main surface-contact placed at some distance
behind it, and an auxiliary skate secured to the car near the axles of the wheels
thereof which auxiliary skate makes electrical contact with the said auxiliary studs
in succession substantially as and for the purpose described.
2. In an electric traction system of the kind described a series of auxiliary studs
each adapted to be temporarily connected through the mechanism of one of the
switches to the main surface-contact placed at some distance behind it, and an
auxiliary skate secured to the car near the axles of the wheels thereof, which auxiliary
skate makes electrical contact with the said auxiliary studs in succession substantially
as and for the purpose described.

page_text: 3. The modifications of the invention for adapting the same to systems in which
the cars run on one track in either direction, substantially as described.
Dated the 4th day of May 1898.
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicants.