Improved Means for Supplying Electricity to Electrically Propelled Railway and Tramway Vehicles.
Year: 1894

page_text: Date of Application, 8th Dec., 1994-Accepted, 2nd Mar., 1895
COMPLETE SPECIFICATION.
Improved Means for Supplying Electricity to Electrically Propelled
Railway and Tramway Vehicles.
I, ALFREDO DIATTO, of 12, Piazzo Gran Madre di Dio, Turin, Italy,
Engineer, 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 :-
This invention of improved means for supplying electricity to electrically
propelled railway and tramway vehicles has reference to apparatus of the kind in
which each vehicle to be propelled is equipped with means for receiving the
electric current, by means of magnetic induction, from an underground conductor
or conductors, by sliding over suitably insulated contact-pieces located at suitable
intervals over a subway and preferably extending slightly above the surrounding
surface of the ground, these contact-pieces being adapted through the medium of
suitable circuit-closing devices beneath the same, and within the subway, to be
placed in communication with an electric conductor in the subway simultaneously
with the passage of the vehicle over the said contact-pieces, the said circuit-closing
devices being enclosed within a casing constituting a part of the subway.
Now according to this invention, the magnetic induction aforesaid is produced
by means of a magnetized bar which possesses a polarity of like sign throughout
its length which may be about equal to that of the vehicle and is greater than the
distance between two consecutive contact-pieces. This bar is arranged to be
brought into contact with a soft-iron switch-block in electrical connection with the
underground conductor, the said switch-block being attracted by the aforesaid
contact pieces as the polarized bar on the vehicle slides over them, the said switch-
block falling back into its position of rest, in consequence of the cessation of the
magnetic action of the bar, when the magnetized bar is carried by the vehicle clear
of the corresponding contact-piece.
The attraction of the soft-iron switch-block by the contact-piece can be facilitated
by establishing communication between it and the underground cable through a
body of mercury, a portion of which the switch-block displaces when in its normal
position, the weight of the part of the mercury thus displaced being about equal to
that of the switch-block. The weight of the switch-block is thus almost entirely
counterbalanced at the moment at which attraction is set up, and when the switch-
block is drawn into contact with the contact-piece it displaces very little mercury
and its weight is thus counterbalanced only to a slight degree, so that it readily
returns to its position of repose.
Important objects of the invention are to ensure the breaking of the circuit upon
the happening of an accident of any description; to reduce to a minimum the
number of insulated points, the amount of insulating material required, and the
number of points at which the current is fed; and to reduce the cost of installation.
The technical advantages appertaining to my improvements will appear from a
consideration of the following description.
In the accompanying drawings,
Fig. 1 represents, diagrammatically, the general arrangement of an electric
traction system embodying my invention;
Fig. 2 is a vertical cross section to a larger scale, showing the switch-mechanism
and the casing enclosing the same; and
Fig. 3 is a vertical sectional view to a still larger scale, showing the switch-block
in its normal position and the connection between it and the underground conductor;

page_text: .
this fig. also shows in elevation a portion of a projection hereinafter referred to
which depends from the contact-piece.
S indicates the carrying rails, K the underground conductor for the electric
current, and A, A1, A2, A3, A", a series of road contact devices for feeding the
current from the underground conductor K to an iron bar a on the vehicle to be
propelled, one of these contacts being shown on an enlarged scale, in Fig. 2.
Gindicates the dynamo for supplying the current, E an electro-motor on the
vehicle, and M the electro-magnets also on the vehicle, by which the bar a is
magnetized...
-
The electro-magnets M, the number and position of which may be varied, are
excited by means of a shunt circuit m and they all impart to the bar a polarity of
like sign. The electro-magnets M are placed between the bar a and an auxiliary
bar the two bars and magnets being rigidly fastened together so as to form a
truss which is adapted to be conveniently secured under a vehicle so as to be
carried thereby and to be insulated therefrom.
The switch-mechanism is enclosed in a casing p, beneath which is located the
conduit for the electric cable K as shown in Figure 2. A part 6 of the top of the
casing p is composed of soft iron and serves as a contact-piece and as a medium
through which the magnetic force of the bar a attracts a circuit-closing device d,
which will hereinafter be referred to as a switch-block.. The contact-piece >>
projects above the ground sufficiently to permit the polarized bar a, which serves
to collect the current, to efficiently slide in contact therewith. The contact-piece b
is provided on its under surface with a projection c, which attracts the switch-block d,
as will be presently explained.
i
.1
1.
The contact-piece is insulated magnetically and electrically from the remaining
metallic portion of the casing p by suitable means such as suitably prepared
wooden blocks and strips of pure rubber g, as shown in Figure 2.
A piece (Figures 2 and 3) serves to unite the wires of the adjacent lengths of
cable K and also as the feeder for the current. Its upper end is made of.conical
form and is adapted to receive the lower end of a reservoir e containing. mercury.q,
into which the switch-block dis- arranged to dip. The attraction of the switch-
block by the contact-piece is effected owing to the fact that as the magnetized
bar a slides over the contact-piece b, the projection c will become magnetized.
The contact surfaces of the projection c and switch block d, may be each provided
with a thin plate of metal such as copper or zinc to serve the double purpose of
reducing liability to oxidation and ensuring the ready return of the switch block to
its original position by gravity as soon as the magnetic attraction of the bar a
In this case
ceases. Or the said contact surfaces may be plain magnetic surfaces.
the block d may advantageously be provided in its upper end with a recess.or
cavity partly filled with mercury into which a pointed extension of the projection c
will dip when the said block is raised by the magnetic attraction of the said
projection; due to the presence above.the projection of the magnetised bar a on the
vehicle. The circuit-closing mechanism is entirely enclosed by the casing p the
atmosphere within which is the only insulating material employed to normally
insulate the contacts from each other.
It will be seen that the switch-block dis attracted by the contact-piece 6 only
while the bar a is in 'sliding-contact with the said contact-piece, and that the
switch-block d will fall back into its normal position when the magnetized.bar.a is
carried by the vehicle clear of the particular contact-piece b. The contact-pieces b
are arranged at uniform distances apart, the distance between successive contact-
pieces being somewhat less than the length of the bar a, so that in operation the
circuit is always closed but only through the medium of the particular contact-piece
or contact-pieces that is or are for the time being covered and protected by the
vehicle.
If, owing to accidental breaking of the circuit, a vehicle should come to a standstill,
it could be promptly set in motion again by exciting the switch mechanism with a
sufficiently strong magnet to produce a temporary connection between it and the

page_text: bar a of the said vehicle. By means of such temporary connections, parts of the
apparatus can be readily exchanged without interfering with the motion of
the vehicles on the line.
In order to reduce the cost of installation of the underground feed-conductors it
is possible to readily combine with this system of feeding the current a system of
three conductors; it is also possible to make use of electro-motors employing
alternate currents and to employ these currents at a high potential while suitably
disposing the contact bars which travel with the secondary conductors upon the
contact pieces b.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. In apparatus of the kind herein referred to for supplying electricity to
electrically propelled railway and tramway vehicles, the use on the vehicle to
be propelled, of a magnetic contact bar a of greater length than the distance
between two consecutive road contact pieces and having the same polarity
throughout its length, the said bar being arranged to slide in contact with the
several road contact pieces in succession and thereby attract the corresponding
switch devices into the operative positions, the arrangement being such that cach
switch device upon being attracted will be held in the closed or operative position
during the whole of the time that the bar a is in contact with the corresponding
road contact-piece and will fall back into its normal and inoperative position when
the bar a passes out of contact with the corresponding contact-piece, substantially
as hereinbefore described with reference to the accompanying drawings.
2. In apparatus for supplying electricity to an electrically propelled railway or
tramway vehicle, a circuit closer or switch-block d of magnetic material
permanently connected with the underground conductor or conductors K through
the medium of a quantity of mercury 9 of which it normally displaces an amount
approximately equal to its own weight, so that the weight of the said circuit closer
or switch-block is counterbalanced, or approximately so, when attraction is set up,
substantially as hereinbefore described with reference to the accompanying
drawings.
3. My improved apparatus for supplying electricity to electrically propelled
railway or tramway vehicles, constructed and arranged as hereinbefore described
and shown in the drawings annexed.
'ונימ
OL of December 1894
F. WISE HOWORTH,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.