Improvements in Apparatus for Controlling Electric Currents.
Year: 1890

page_text: Date of Application, 18th Nov., 1890-Accepted. 20th Dec., 1890
COMPLETE SPECIFICATION.
Improvements in Apparatus for Controlling Electric Currents.
I, RALPH HENRY CHRISTOPHER NEVILE J.P., of Crown Lea, Malvern in the
County of Worcester, Gentleman, 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 :-
My invention relates to an apparatus to be inserted in any electrical circuit to
allow of the current flowing through the said circuit in one direction only or rather
of inserting a considerable resistance if it should flow in the other direction.
One of the principal uses to which this apparatus is applied is to prevent the current
from a battery of electrical accumulators flowing back through the dynamo if for any
reason the electro-motive force of the dynamo should fall below that of the batteries
that it has previously been charging-but it may also be applied in any case where it
is desirable that the current in a particular main should flow through it in one direction
only.
For this purpose I use a magnet which may be a permanent one or it may be an
electro-magnet excited from any source which will keep its poles permanently the
saine. This magnet is suspended in such a way that it is free to move and either one
or both of its poles are in proximity to a pole or poles of one or more electro-magnets.
This electro-magnet or electro-magnets are wound with two separate windings one of
fine wire of a size proportioned to the maximum difference of electro-motive force
which is likely to arise between the torminals of the apparatus and the other of thick
wire capable of carrying without offering an undue resistance the whole of the current
passing through the apparatus.
To the moveable magnet is attached a contact piece which makes contact between
one end of this latter coil of wire or copper strip and one of the main terminals of the
apparatus and preferably form this contact piece of a copper fork which in oue
position of the magnet dips into two cups containing mercury, one of the cups being
in electrical connection with the end of the coil of wire above mentioned and the other
cup in electrical connection with the terminal of the apparatus, and in the other
position of the moveable magnet is withdrawn from the mercury in the said cups thus
severing the connection. The other end of the large sized coil of wire is connected
to the other terminal of the apparatus.
The fine coil of wire has one of its ends attached to each main terminal of the
apparatus.
If now the electro-motive force at one terminal say A of the apparatus is higher
than that at the other terminal say B, (the two terminals being supposed to be
connected together through an independent exterior circuit) the current will flow
through the fine wire from A to B and will cause the poies of the electro-magnet to
assume such polarity as will cause the moveable magnet to assume such a position as
will close the main circuit between the terminals and through the large coil of wire
by means of the contact piece. On this being done the fine wire coil is short
circuited by the large wire coil of much lower resistance through which the main
current immediately flows retaining the electro-magnet or magnets of the same
polarity and consequently retaining the contact piece in the same position. If now
the electro-motive force at A falls so as to be below that at B the current tends to
return in the opposite direction and the electro-magnets first loose their polarity
altogether and then tond to assume opposite polarities, as this happens the moveable
magnet is operated upon in a contrary sense and the contact piece is withdrawn from
the mercury cups severing the connection except through the fine wire coil of high
resistance. This retains the contact piece in the off position until such time as the
electro-motive force at A again rises above that at B when it again reverses its action
and closes the main circuit.

page_text: In the accompanying sheet of drawings
Figure 1 is the type of apparatus that I generally prefer to use in which the electro-
magnet is of a horse shoe type, one pole of the moveable magnet being placed between
the two poles of the horse shoe clectro-magnet.
A and B are the two terminals, is the electro-magnet wound with a large sized
wire one end being connected to terminal A. and the other to the mercury cup M, also
with a fine wire one end of which is connected to terminal A and the other to
terminal B. This is shown by a dotted line. The winding and connections of these
two must be such that if the current passes from A to B through the fine wire or
through the large wire and mercury cups the poles of the electro-magnet will remain
of the same polarity.
Suppose it is desired that the current should flow in at A. and out at B and not in
the reverse direction-the coils of the electro-magnet being so wound that a current
flowing from A to B will induce a north pole at D and a south pole at E. The
permanent magnet will be so magnetised that it has a south pole at G. This
permanent magnet is pivoted at E and attached by a strip K of some suitable
material to the copper fork L, which is preferable insulated by any convenient means
from the magnet G. As long as the electro-motive force at B is higher than that at A
the current Hows through the fine wire coil in the direction B, A, causing a south
pole at D and a north pole at and pulling downwards the south pole of the
permanent magnet thus keeping the fork L out of the mercury cups M', M²; on the
electro-motive force of A rising sufficiently above B, the action is reversed and
the poles of the electro-magnet are reversed but as tho pole of the permanent magnet
remains the same it is now attracted by the upper pole D and repolled by the lower
pole E thereby lowering the fork L into the mercury cups M, M. This action closes
the main circuit and short circuits the fine wire coil and the polarity of the
electro-magnet is maintained by the main current flowing through the large wire
coil.
F F are two small brass pins for the purpose of limiting the travel of the moveable
arm and preventing the moveable magnet coming in actual contact with the soft iron
poles D and E.
It may also be necessary to attach an adjustable weight to the magnet G. or arm K
in order to produce such a state of equilibrium that the fork L when the electro-
magnet C is not excited in either direction will just lift itself out of the mercury in
the cups.
Figure 2 is a diagram showing the manner the apparatus may be connected up
when the object of using it is to prevent the current from a battery of electric
accumulators flowing back through the dynamo.
It is obvious the apparatus may be made in various other ways for example the
permanent magnet may be prolonged and its other end acted upon by another electro-
magnet of the horse shoe type or an electro-magnet with a single acting pole may be
provided at each end, and if separate magnets are used if desired one may be wound
with the fine wire and one with the thick wire or they may both be wound with two
wires and these wires may be connected together as may be most convenient thus
both the fine wire coils may be in series and both the large wire coils in parallel or
vice versa.
In addition to the above arrangement I sometimes use an electric bell which is so
constructed that when the clapper of the bell is attracted towards the bell the electro-
magnet so attracting it is short circuited thus releasing the clapper and thus producing
a trembling stroke. In this case I sever the fine wire between B and A and insert
this bell in the circuit, the result being that as long as a sufficient potential difference
between A and B is maintained the bell rings giving warning of the fact that the
switch is not closed. Or I can cause the electro-magnet to make a contact with an
ordinary electric bell when in the off position.
Further in either case instead of connecting the bell directly I can use a relay and
cause the relay to ring the bell and if this relay is connected in the fine wire circuit B
to A I can use a polarised relay so that it will either ring the bell only when the

page_text: current is passing through the fine wire coil in one direction or I can cause it to ring
two bells one for one direction and one for the other.
Instead of bells I can use any other form of indicator either sounding or visual
that may be desirable and that can be conveniently actuated by an electric
current.
In some cases it is desirable to insert a small fuse wire in the circuit B A so
that should the electro-motive force from any cause rise too high and the switch
fail to close itself properly the circuit would be broken and the fine wire coil be
uninjured.
In conclusion I say that I do not confine myself precisely to the forms above
described but that what I do claim is
1. In an apparatus for controlling the flow of an electric current in one direction
by means of an electro-magnet or electro-magnets and a moveable arm substantially
as above described, the use of two wires connected in such a way that when the main
circuit is closed and the current flowing principally through the larger wire the
smaller wire will be short circuited by the larger wire and have only a very minute
fraction of the total current flowing through it.
2. The use in conjunction with apparatus for the above purpose of an electro-
magnet or magnets of a horse shoe form between the poles of which the moveable
magnet vibrates.
3. The use in conjunction with apparatus for the above purpose of a bell or bells or
any indicating apparatus substantially as described for the purpose of indicating the
action or non-action of the apparatus.
4. The use of apparatus substantially as above described for preventing or reducing
the flow of an electric current through an electric circuit in one direction.
Dated this 18th day of November 1890
JOHN P. O'DONNELL,
2, Great George Street, Westminster, London, S.W.,.
Agent for the said Applicant.