Improvements in and relating to Surface Contact Electric Railway Systems.
Year: 1897

page_text: Date of Application, 7th Sept., 1897-Accepted, 13th Nov., 1897
COMPLETE SPECIFICATION.
Improvements in and relating to Surface Contact Electric Railway
Systems.
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 or closed conduit systems of supply
for electric railways; and has for one of its objects to provide efficient means for
preventing the vitalizing of contacts in the street surface after or before a car
passes, by leakage current holding up the switches when the car is not near. It
also has for its object to provide a simple and efficient way of vitalizing the high-
potential contacts immediately in advance of the car so as to allow the switches
to close before the current is taken from the contact, and thus avoid liability to
failure of current.
In fully describing the invention reference is made to the accompanying
drawings which illustrate same in diagram. Fig. 1 is a diagram of an arrange-
ment employing two coils upon a switch, and Fig. 2 one in which three coils are
employed
In Fig. 1, A, A, are the track rails furnishing the ground of the system; B, B¹
are the high-potential studs connected by the switches G, G1, G2 and so on, to
the feeder H. It will be observed that none of these connections carries any
coil, the connections from the feeder to the stud being direct. C, C are low-
potential contacts for energizing the switches G, G1, G2 and so on. D), D¹ are
the car wheels, E is a storage battery: M, M are the motors carried upon the
vehicle. F, F are the shoes for making contact. Each of the switches G, G¹, G
is provided with two coils g', g, and contacts g, g', which are bridged when the
switch is closed. The coil g of each switch is in circuit between its own low-
potential contact and ground, while the coil is in circuit between the low-
potential contact of the switch next adjacent and ground. The two coils are
connected in multiple and have separate grounds, for reasons presently to be
pointed out. The operation of the devices shown is as follows:
Assuming that no current is flowing in the motors, the current would flow from
the storage battery E to the shoe ; as the car moves to the left, this shoe
would pass from its illustrated position to the contact C, sending current through
the coil on the switch G, and picking up that switch, energizing the stud B
in advance of its contact with the shoe F. The current from the battery divides
and a part of it passes through the coil g³ on the switch G, holding up this latter
switch, so that the shoe F takes current from the stud B' until the shoe F¹ has
broken contact with the stud C. As soon as current begins to flow, the storage
battery E may be cut out, as the motor current will then operate the
switches G, G¹. It will be observed that all the coils upon the switches are
upon the negative side of the motors.
In Fig. 2 the same parts are shown, except that each of the switches G has an

page_text: additional coil 9. The coil g³ is in circuit with a low-potential stud upon one
side of the switch, and go with a similar stud unon the other side, while g' is in
circuit with the stud of its own switch. Thus when the shoe F is in contact,
as illustrated, with the stud C, current from the battery or from the motor, as
the case may be, passes through the coil to ground, closing the switch G.
Dividing, it also passes through the coil g³, closing the switch G2, and through
the coil g to close the switch G. As before each of these coils has separate
ground.
The object of separately grounding each of the coils is to protect the apparatus
against the effect of leakage through a low-potential stud. If the coils were con-
nected to a common ground wire, and this ground wire were broken between this
junction and ground, then any leakage through one of the low-potential studs,
for instance the stud C of Fig. 1, would serve to pick up switches beyond those
intended. Assume for instance that the coils g, 9 upon the switch G¹ had a
common ground connection, and this were broken, then current from the stud C
would pass first through the coil go, picking up the switch G, then by the con-
nection between the coils through coil g' upon the same switch G³ thus neutralis
ing the coil g and opening that switch, and then to the coil g5 upon the switch G+³,
picking up that switch, and energizing the high-potential stud 133, the second one
away from the one designed.
A similar result would be manifestly obtained in Fig. 2 should the three coils
of the switches shown in that figure be connected by a common wire to ground
in case the wire should break; in this case studs in both directions from the car
beyond those intended would te energized, with consequent danger to persons
and teams passing either in front of or behind the car.
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:-
1. A surface contact electric railway system, comprising a feeder, track rails,
and sectional conductors in the roadway, with electro-magnetic switches serving
to make temporary connection in sequence between the feeder and the sectional
conductors, the switches connected between the negative side of the system and
ground by coils in multiple upon the different switches.
2. A surface contact electric railway system, comprising a feeder, track rails,
and sectional conductors in the roadway, with electro-magnetic switches serving
to make temporary connection in sequence between the feeder and the sectional
conductors, the switches connected between the negative side of the system and
ground by coils in multiple upon the different switches, each coil having an inde-
pendent ground connection, in combination with a vehicle moving on the line of
way, and making travelling contact with the sectional conductors, provided with
motors in circuit between the travelling contacts, and a storage battery.
3. A surface contact electric railway, comprising track rails, sectional cou-
ductors, a feeder, and electro-magnetic switches for making connection between
the feeder and the sectional conductors in sequence; each of the switches furnish-
ing current to a single contact or conductor in the roadway, and being provided
with operating coils in multiple with more than one of the sectional conductors
upon the negative side of the system, each of the coils upon the switch being
separately grounded for the purpose set forth.
Dated this 7th dor of Condomhan 100%