Improvements in and relating to Surface Contact or Closed Conduit Electric Railways.
Year: 1897

page_text: This Print is in accordance with the Original Specification as it stands after
Amendment (under Section 11 of the Patents, &c. Act, 1883) as required by
the decision of the Chief Examiner, of the 21st day of June 1898.
Date of Application, 7th Sept., 1897-Accepted, 27th Nov., 1897
COMPLETE SPECIFICATION (AMENDED).
Improvements in and relating to Surface Contact or Closed Conduit
Electric Railways.
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of this
invention (which has been communicated to us from abroad by William B. Potter,
of Schenectady, County of Schenectady, State of New York, United States of
America), and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
This invention relates to surface contact systems of supply for electric railways,
and has for its object to provide for such systems a safety device by which any
leakage current will serve to open a switch which may by accident have remained
closed, instead of increasing (as in most other systems) the danger of the switch
sticking.
-O
To accomplish the purposes of the invention all the contact studs or sectional
conductors both + and are surrounded with metallic boxes or enclosing bands,
and the bands or boxes are connected to the wire or return circuit through indepen-
dent coils upon independent pull-down magnets acting on the same switch. Any
leakage current seeking ground through such a box and its lead will pass through
the coils and demagnetize and open the switch. In the practice of the invention
we use both high potential and negative studs or contacts and each one of both
of these sets of sectional conductors is provided with the device mentioned.
The accompanying drawing shows the invention, it being a diagram showing
five of the safety devices and their connections.
A, A are the track rails; B to B, C to C, respectively the high potential and
negative sectional conductors or contacts; H the feeder; G, G₁ are the pick-up
switches, provided with magnets having operating or pick-up coils, and con-
tacts g, g, g, by which the connection from the feeder H to the positive studs B, B¹
is completed. A motor car provided with motors M, M, and a storage battery E,
also sliding contacts F, F, travels upon the line of way.
At I, I surrounding, but insulated from the positive contacts B, B' are indi-
cated diagrammatically the safety grounds, consisting of metal boxes connected
each through coils ³, respectively upon the pull-down magnets of the
switches G, G¹ to ground. Each of these contacts is thus connected to one of the
switches and any leakage current from the box will open the switch.
At L to L' are shown the safety devices applied in the same way to the nega-
tive sectional conductors C to C+ which are grounded (as in the case of the studs B)
respectively through the differential coils go go upon each of the pull-down magnets
of the switches G to G. As before, any leakage current which ordinarily would
reach the stud C and by passing through the pick-up coil pick up the switch,
D....631

page_text: is now intercepted by the box I, and should any leakage current arrive at the
stud C it will be intercepted by the box L. Such leakage currents then pass
through the coils gg and serve to hold the switch G open, or to open it if it
should be stuck. The power of the coils is of course to be porportioned to the
work to be done and ordinarily the auxiliary coils serving to demagnetize and
open the switch would have less power than the pickup coil, inasmuch as the
leakage current would necessarily be of comparatively small volume and moderate
potential, while the pick up coil would carry full current.
We are aware of the Specification of Letters Patent granted to David Urquhart
and Frank Wynne, No. 24578, A.]). 1895, and we lay no claim to anything
described and claimed therein nor do we claim the system of operating the
switches shown in this case but having now particularly described and ascertained
the nature of the said invention (as communicated to us from abroad) and in
what manner the same is to be performed, we declare that what we claim is:
In an electric railway, in which there are a distributing circuit composed of a
positive feeder and ground return, and two sets of sectional conductors, switches
for connecting the sectional conductors with the positive feeder, and pick-up
electro-magnets connected to ground, and to the second set of sectional conductors
for closing said switches, the combination with leakage boxes I, I, I, I, I and
80 on, of leakage boxes L, L1, L2, L³, L, and so on, said boxes surrounding both
the sets of sectional conductors or contact studs, and pull-down magnets arranged
beneath said pick-up switches, said magnets having their coils connected with
both sets of leakage boxes and with the ground return for opening the circuit
between the positive feeder and the sectional conductors, as above described and
the diagram.
Dated this 7th day of September 1897.
For the Applicants,
J. C. CHAPMAN,
Chartered Patent Agent, 70, Chancery Lane, London, W.C.