Improvements in Closed Conduit Electric Railways.
Year: 1897

page_text: Date of Application, 26th Jan., 1897--Accepted, 27th Feb.. 1897
COMPLETE SPECIFICATION.
Improvements in 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 Edwin W. Rice,
Junior, 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 :-
Our invention relates to surface contact or closed conduit systems of electric
railways; and has for its object to provide a means of preventing the energizing of
the street contacts at a time when they are not covered by the car, and to thus
prevent damage to persons and vehicles crossing the line of way.
One source of difficulty which engineers have sought to avoid has been leakage
from the high potential studs or contacts carrying the motor current to the contacts
which serve to pick up the electro-magnetic switches commonly proposed. It is
manifest that where leakage occurs in this way, it will tend to hold up the switch
and energize the contacts not covered by the car. By our invention this is prevented
by interposing between the high potential contacts a ground adjacent to and
surrounding the low potential stud, so that any current that may leak will not reach
the stud but will be diverted to ground, and the switch will be free to open in the
usual way.
"
Our invention is illustrated in the accompanying drawings, in which Fig. 1 is a
diagram of circuits which may be employed, it being typical of any operative
arrangen ent; and Fig. 2 is a section of the proper mechanical construction.
In Fig. 1 A, A, are the track rails upon which the car, represented by the
wheels D, D', moves. M, M, are the motors connected between the sliding shoes or
contacts F, F' carried by the car. E is a storage battery connected between the
ground and one of the shoes. The high potential studs are lettered B, B¹, &c., and
serve to carry current to the motor by way of the shoe F. The low potential studs
or those in circuit with the coils of the pick-up magnets are lettered C, C³, &c., the
coils themselves being lettered g*, g³. The pick-up magnets serve to close the
switches G, G' at the contacts 91, 92, energizing the high potential studs B, &c. It
will he observed that each stud C is connected through coils on two switches to
ground, so that energizing one stud picks up two switches. The high potential and
low potential contacts or studs are "staggered," so that the switch is closed before
the contact with the motor circuit is made.
The operation of these parts is as follows: As the shoe F¹ touches in succession
the low potential studs, the switches pick up, energizing the high potential studs
and carrying current to the motors. The motor current is carried directly through
the low potential studs and the coils on the pick-up magnets to ground. When
however the current is cut off from the motors, all the switches fall, and when it is
desired to start the car, the current is passed from the storage battery through the
low potential studs with which the shoe F¹ happens to be contact, picking up the
switches which will then be held up by the motor current. Adjacent to each of
the studs C we arrange a surrounding box provided with an independent ground
connection. This is best seen in Fig. 2.
In that figure A is, as before, the track rail; m is the ground connection to the
rail from the metal box c surrounding the low potential stad C. The connection to

page_text: the circuits is seen passing through the box, being protected by an insulating
bushing. The contact stud itself is carefully insulated from the surrounding box by
insulation c¹.
It is manifest that our invention may take many forms. The one we have shown
is well adapted to its purpose and the essential feature of our invention consists in
the furnishing of an independent ground connection adjacent to and serving to
protect the pick-up contact magnets so that leakage current would be intercepted
before it reached the coils of the pick-up magnets. It is also manifest that the
independent ground connection will sufficiently serve its purpose if it be interposed
at any point between the high potential stud and the pick-up magnet, it being of
course necessary to insulate it from the high potential stud; the fundamental
feature of the device being a shunt circuit to ground for leakage currents, by
which such currents are kept away from the coils on the pick-up magnets. It
is further manifest that the invention finds its utility in those cases in which the
magnet coils are grounded at one end.
Having now particularly described and ascertained the nature of this inven
tion (as communicated to us from abroad) and in what manner the same is to be
performed, we declare that what we claim is :
1. In a surface contact or closed conduit electric railway system, an independent
ground connection adjacent to the pick-up magnet contacts and adapted to protect
the coils on the pick-up magnets from extraneous or leakage currents, substantially
as set forth.
2. In a surface contact or closed conduit electric railway system, a metal box
surrounding the low potential pick-up magnet contact and insulated therefrom, with
an independent ground connection from the box, the whole adapted to protect the
pick-up magnet coils from extraneous or leakage current.
3. In a surface contact or closed conduit electric railway system provided with
sectional conductors and grounded coils upon the pick-up magnets connected to the
sectional conductors, an independent shunt circuit to ground for leakage current,
interposed between the high potential studs and the contacts connected to the magnet
علنمه
Dated this 26th day of January 1897.
For the Applicants,
J. C. CHAPMAN,
70, Chancery Lane, London, W.C., Chartered Patent Agent.