Improvement in Electric Tramways and Railways.
Year: 1887

page_text: Date of Application, 14th Nov., 1887
Complete Specification Left, 14th Aug., 1888
Complete Specification Accepted, 21st Sept., 1888
Improvement in Electric Tramways and Railways.
I, BENJAMIN JOSEPH BARNARD MILLS carrying on business under the firm or
style of Harris and Mills of 23 Southampton Buildings, in the County of Middlesex
Patent Agent, do hereby declare the nature of this invention, a communication to me
from abroad by Thomas Alva Edison of Llewellyn Park, in the County of Essex
and State of New Jersey, United States of America, Inventor, to be as follows:-
Heretofore great difficulty has been experienced in properly insulating the contact
conductors of electric tramways and railways, such conductors being those with which
travelling electrical contacts are maintained at the moving cars. This difficulty arises
from the necessity of using high tension currents in order to secure economy in
working. The losses from leakage due to imperfect insulation have been especially
great when the contact conductors are at the surface of the ground as when the
traffic rails upon which the cars travel are used as such conductors in whole or in
part, or when one or more other rails between the traffic rails are so used alone or in
conjunction with the traffic rails. For the street tramways of cities and towns,
this difficulty has caused the resort to the use of one or more contact conductors
elevated above the cars by supports, or to slotted conduits sunken between the rails
and carrying the contact conductors therein; but both of these methods are highly
objectionable.
The object of the present invention is to overcome largely the loss from leakage
upon the contact conductors of electric tramway and railways. The invention is
applicable to electric tramways and railways whatever may be the arrangement or the
construction of, or the method of supporting the contact conductors but it has the
especial advantage of permitting the use for the contact conductors of surface
conductors such as the traffic rails, or a central rail and the traffic rails, or two
central rails without the traffic rails.
This end is accomplished by using a current of the desired high tension on conductors
running parallel with the tramway or railway, and by connecting such conductors at

page_text: short intervals with the contact conductors of the tramway or railway through tension-
reducers, so that upon such contact conductors the current will have a very low
tension, say, for illustration, from five to ten volts, while the tension of the current on
the main supplying circuit may be as great as desired.
It is proposed to employ any of the various forms of tension-reducers shown in the
specifications of patents granted to T. A. Edison, such tension-reducers being
preferably connected with the main circuit in multiple arc; It is preferred to employ
continuous currents upon the main supplying conductors as well as upon the contact
conductors, and to use as the tension-reducers combined generators and motors,
although any other means for converting currents may be employed, or alternating
currents upon both sets of conductors may be employed with suitable generators and
motors therefor, and simple induction coils without working parts be used for reducing
the tension as will be well understood. The contact conductors may be continuous
from end to end of the tramway or railway, but it is preferred to divide them into
sections with a tension-reducer connected with each section, so that the secondary
circuit of each reducer will be open except when a car is travelling over the section
with which it is connected.
Electrically or mechanically operated switches may be provided for connecting
and disconnecting the sections of the contact conductors as the car advances. The
electric motor of each car will be in a separate cross or multiple arc circuit from the
contact conductors and all of such car motors will be properly proportioned in their
winding and construction for efficient working with low tension currents. The main
conductors may be run on poles or buried underground, and the tension reducers may be
located at any convenient points: such tension-reducers may be placed in water-tight
man-holes constructed at intervals by the side of the tramway or railway. The
generators may be connected directly with the main circuit, or by means of feeders to
better distribute the current.
Dated th: 1421 1
Car
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I, BENJAMIN JOSEPH BARNARD MILLS carrying on business under the firm or
style of Harris and Mills of 23 Southampton Buildings in the County of Middlesex,
Patent Agent, do hereby declare the nature of this invention, a communication to
me from abroad by Thomas Alva Edison of Llewellyn Park, in the County of Essex
and State of New Jersey, United States of America, Inventor, and in what manner
the same is to be performed, to be particularly described and ascertained in and by
the following statement :-
Heretofore great difficulty has been experienced in properly insulating the contact
conductors of electric tramways and railways, such conductors being those with
which travelling electrical contacts are maintained at the moving cars. This difficulty
arises from the necessity of using high tension currents in order to secure economy in
working. The losses from leakage due to imperfect insulation have been especially
great when the contact conductors are at the surface of the ground as when the traffic
rails, upon which the cars travel are used as such conductors in whole or in part, or
when one or more other rails between the traffic rails are so used alone or in con-
junction with the traffic rails. For the street tramways of cities and towns, this
difficulty has caused the resort to the use of one or more contact conductors elevated
above the cars by supports, or to slotted conduits sunken between the rails and
carrying the contact conductors therein; but both of those methods are highly
objectionable.
The object of the present invention is to overcome largely the loss from leakage
upon the contact conductors of electric tramways and railways. The invention is
applicable to electric tramways and railways whatever may be the arrangement or the
construction of, or the method of supporting, the contact conductors, but it has the
especial advantage of permitting the use for the contact conductors of surface
conductors such as the traffic rails, or a central rail and the traffic rails, or two central
rails without the traffic rails.
This end is accomplished by using a current of the desired high tension on
conductors running parallel with the tramway or railway, and by connecting such
conductors at sbort intervals with the contact conductors of the tramway or railway
through straight current tension reducers, so that upon such contact conductors the
current will have a very low tension, say, for illustration, from five to ten volts, while
the tension of the current on the main supplying circuit may be as great as desired.
It is proposed to employ any of the various forms of tension reducers shown in the
specifications of patents granted to T. A. Edison and producing straight currents or
those of one direction in the secondary circuit, such tension reducers being preferably
connected with the main circuit in multiple arc. It is preferred to employ continuous
currents upon the main supplying conductors, as well as upon the contact conductors,
and to use as the. tension reducers combined generators and motors, although any
other means for converting straight currents may be employed. The contact
conductors may be continuous from end to end of the tramway or railway, but it is
preferred to divide them into sections with a tension reducer connected with each
section, so that the secondary circuit of each reducer will be open except when a
car is travelling over the section with which it is connected.
Electrically or mechanically operated switches may be provided for connecting and
disconnecting the sections of the contact conductors as the car advances. The electric

page_text: motor of each car will be in a separate cross or multiple arc circuit from the contact
conductors and all of such car motors will be properly prortioned in their winding
and construction for efficient working with low-tension currents. The main conductors
may be run on poles or buried under ground, and the tension reducers may be
located at any convenient points; such tension reducers may be placed in water tight
man holes constructed at intervals by the side of the tramway or railway. The
generators may be connected directly with the main circuit, or by means of feeders
to better distribute the current.
In the accompanying drawings forming a part of the present specification:
Figure 1 is a view principally in diagram illustrating the principle of the
invention; and
Figure 2 is a sectional view showing the location of a tension reducer in a man
hole with the connections thereto and therefrom.
A represents one or more continuous or straight current generators of electricity,
which may be one or more continuous current dynamo electric machines as before
explained. These generators may be located at a station at any point upon the line
of the tramway or railway. Conductors 1. 2. extend from A to the conductors 3. 4.
of the main circuit, which extend along the line of the tramway or railway. To this
main circuit is supplied a straight current of high tension. Separate multiple arc
circuits 5. 6. extend to tension reducers B, from which extend conductors 7. 8. to
the contact conductors 9. 10. These contact conductors are shown as the traffic rails
upon which the cars () carrying electric motors D travel, such motors being properly
proportioned for low tension currents. The tension reducers produce upon the
contact conductors a straight current of low tension. The contact conductors are
shown in Figure 1, as divided into sections by insulation a, one tension reducer being
connected with each section, although the contact conductors may be continuous as
before explained.
The tension reducer B of figure 1 may be considered as any known form of
apparatus for converting a high tension straight current into a low tension straight
current.
In figure 2, the tension reducer B is a combined_motor and generator adapted to be
operated by and to produce continuous currents. It is located in the water tight man
hole E and is connected with the main conductors and with the working conductors
as shown.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what
I claim is :-
An electric tramway or railway, wherein are combined moving cars provided with
electric motors proportioned for operation by low tension straight currents, contact
conductors with which the cars make a travelling contact, a main supplying circuit
extending along the line of the tramway or railway and having a current of high
tension, and a number of straight current tension reducers located at intervals along
the line of the tramway or railway and near thereto, such tension reducers being
connected with the said main supplying circuit and with the said contact conductors
and producing a straight current of lower tension upon the latter substantially as
hereinbefore specified.