Improvements in Electric Surface Contact Tramways.
Year: 1898

page_text: Date of Application, 28th Nov., 1898
Complete Specification Left, 26th Aug., 1899-Accepted, 30th Sept., 1899
I, SILVANUS PHILLIPS THOMPSON, of Chislett Road, West Hampstead, Doctor
of Science, do hereby declare the nature of this invention to be as follows:-
-
My invention relates to electric surface contact tramways and has for its object
the application of the methods heretofore described by me in conjunction with
Mr. Miles Walker under Patents Nos. 14252, 18416, all of 1897 to cases where
rails are not used as a return circuit. In these cases a return circuit is made through
a second series of road studs arranged parallel to those of the supply circuit,
a second skate or its equivalent being carried beneath the car. The studs of the
return circuit may be connected to work in several ways: (a) with independent
switch mechanism in each as in the supply studs; (b) with switch mechanism
operated by contacts in the switches of the supply studs; (c) without mechanism
but operated by contacts in the switches of the supply studs; (d) by permanent
connexion to an independent return feeder or main, whether wholly insulated
or partially insulated, or not insulated at all from the ground. The return
studs may be provided with guard-plates, or one common guard-plate for a
supply stud and a return-stud may be used.
Dated this 28th day of November 1898.
SILVANUS P. THOMPSON.
FINAL SPECIFICATION.
Improvements in Electric Surface Contact Tramways.
I, SILVANUS PHILLIPS THOMPSON, Fellow of the Royal Society, of "Morland,"
Chislett Road, West Hampstead, in the County of London, 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:
In previous Specifications of Patents, No. 19455A of 1896: No. 14252, and
No. 18416 of 1897, I have described in conjunction with Mr. Miles Walker a
system of electric traction in which surface contacts are successively connected
to a supply main by means of a special kind of automatic switch, therein
described in detail.
The object of this invention is to extend that electric traction system to those
cases in which a separate main instead of the rails is employed for the return
current. For this purpose I lay a second row of studs which I call return studs,
which can be connected successively to the return main. The car carries a
second skate which makes contact with the return studs so that the current
[Price 8d7

page_text: passes from the high potential studs through the first skate to the motor and
thence through the second skate to the return main. In many cases the return
main can be kept at almost earth potential so that there is no objection to the
studs being permanently connected with it.
In the accompanying drawing:
Figure 1 is a diagram illustrating a traction system embodying my present
invention.
Figure 2 is a diagram shewing a modification.
Referring now to Figure 1, F is the outgoing or high potential main, S the
high potential studs, F the return main and S₁ the return studs. M is the car
motor, K the skate co-operating with studs S and K¹ the skate co-operating
with the studs S¹. The studs Si are connected through switch contacts to the
return main and the diagrams are intended to illustrate the case in which the
said switch contacts are operated by the main switches. The main switches are
of the type described in detail in the specifications above referred to the only
difference being that the moving part of the switch carries an additional con-
tact piece represented diagrammatically by G which when the switch is closed
connects the switch contacts the wire joining S¹ to the return main F¹. The
magnetising coil of the switch has one of its terminals connected to the stud S,
while the other terminal is connected either to the rail or to the return main F¹
as shewn in Figure 1, or to the stud S₁ as shewn in Figure 2.
I sometimes connect the return studs S¹, S¹ directly to the return main with-
out the interposition of switch contacts in which case there may be a slight
amount of leakage from the studs when the potential of the return main is above
that of the earth but this slight leakage will be so small as compared with the
leakage and earth current which arises when a rail return is used that such direct
connected stud may be permitted in towns in which the rail-return would not
be permitted.
For convenience in laying the main and to obviate the multiplication of water-
tight glands and the insulation of the switch I sometimes locate the switches
under the studs S¹ S¹ instead of under the studs S S as shewn in the figures of
the specifications above referred to.
In cases where it is desirable I provide independent automatic switches
for connecting the studs S¹ to the return main, such switches being similar in
construction and operation to the switches for connecting the studs S to the out-
going main described in the Patent Specifications hereinbefore referred to.
I also employ the return studs in conjunction with the switches and intercon-
nections described in Specification numbered 19456 of 1896.
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:
1. In an electric tramway system of the kind referred to, the provision of a
second series of contact studs with a co-operating skate carried on the car, said
studs being either permanently connected or automatically connected at the
proper times to the return main, substantially as described.
2. An electric tramway of the kind described with automatic switches con-
structed and operating substantially as described with reference to either of
the figures of the accompanying drawing.
Dated the 26th day of August 1899.
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester, and Birmingham.