Improvements in Telegraphio and other Electro-magnetio- Instruments.
Year: 1896

page_text: Improvements in Telegraphio and other Electro-magnetio-
Instruments.
HERBERT WATSON SULLIVAN, Electrical Engineer, of 29 Ladbroke:Square,
London, W.. do hereby declare the nature of this invention to be as follows:
My invention relates to electro-magnetic instruments of the moving coil type,
principally those with fixed cores, & consists of means whereby the magnetic
resistance is greatly reduced with a corresponding increase of sensibility. This
object I accomplish. by so shaping the poles or pole pieces of my magnet, or the
core or both together, as to bring them into exceedingly. close proximity to each
other, without preventing free play of the coil. In certain cases I employ-one or
more magnets or sets of magnets to still further intensify the field, the core being
of such section as to fulfil the requirements of each case.
I may give my poles or pole pieces. a hollowed out or crescent shaped-section,
the ends or.horns on each side, almost touching the fixed or central-core, & the
hollowed-out space in the poles or pole pieces being sufficiently large-to allow of
the coil swinging freely to any required angle. In certain cases I may make the
poles or pole pieces more or less knife edged, each knife edge all but touching the
core, & the coil moving outside them parallel to their plane..
Sometimes I may employ two such magnets or sets of magnets, the one opposite
the other, & the fixed core, which may be of circular, elliptical or other
convenient section; being thus almost touched in four places. The like poles in
this arrangement are not brought so close together as to unduly attraetor
restrict the play of the moving coil.
To still further intensify the field, I may use a third magnet or system of
magnets with poles so placed in relation to the core, & at such a distance apart
from each other as to allow of free movement of the coil. The poles or pole pieces
of all the magnets must necessarily be in unison-that is to say, all the north poles
must be on one side, & all the south poles on the other.
I may sometimes find it convenient to make the core of my coil in two parts,
beld together by means of screws or other suitable device.
This invention is of important application in the construction, of very sensitive
single current or double current relays, or siphon recording instruments for
submarine cables, but it may also be used to increase the sensitiveness of other
instruments on the moving coil principle.
Dated this 8th day of February 1896.

page_text: Improvements in Telegraphio and other Electro-magnetio
Instruments.
I, HERBERT WATSON SULLIVAN, Electrical Engineer, of 29 Ladbroke Square,.
Notting Hill, in the County of London 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 for improvements in telegraphic and other electro-magnetic
instruments has for its object to concentrate the magnetic field of electrical
measuring or signalling instruments in which a coil is suspended in the field of a
fixed magnet, and consists in reducing the air gap of the magnet by projecting
forwards some or parts of the pole pieces to nearly touch the core of the coil whilet
others or other parts of the said pole pieces are retracted cut away or recessed to
receive and allow of the requisite motion of the coil, and in forming the core of the
inovable or suspended coil of two parts firmly secured together but insulated from
one another.
In carrying out this invention two poles only may be employed, or four or more.
In the case where four poles are employed they may have knife-edge pole pieces,
the coil being free to work between the knife-edges of the pairs. In case six poles
are employed the central pole of each set of three is retracted to allow of the
motion of the coil the outer poles having knife-edges coming into close proximity
with the core of the coil.
. In the accompanying sheet of illustrative drawings;
Fig. 1 shows the poles of a horse shoe or crescent shaped magnet and of the core
having projecting parts according to this invention.
Fig. 2 shows a modification in which the magnetic field is formed by two horse
shoe magnets or four separate poles.
Fig. 3 shows a further modification in which the magnetic field is formed by
three magnets or six separate poles.
.
Referring to Fig. 1 the horse shoe or crescent shaped magnet bhas cach of its
poles p recessed between its extreme edges k as shown at i. The edges k of the
pole pieces p are more or less knife-edged and are in close proximity with the
core a of the coil d which is movable about its axis c. The coil d is free to move
within the recesses i of the pole pieces p but not beyond the projecting edges that
are nearly touching its core. The recesses are sufficiently long to allow of the
swinging of the coil to any required angle.
In the modification shown in Fig. 2 two sets of magnets e and f having knife-
edged poles k are arranged with a small space between their like poles so as to
leave an opening i for the free play of the coil d.
In the further modification shown in Fig. 3 a third magnet or set of poles gh are
placed with like poles in the opening i between the poles of the magnets shown in
Fig. 2 but are set back so as to leave room for the movement of the coil d.
The fixed core a of the movable coil is of elliptical or elongated form and is
formed so that it has four distinct edges just opposite the four edges of the poles
and nearly touching the same. It is made in two parts held together by screws.
This invention is of important application in the construction of very sensitive
single current or double current relays, or siphou recording instruments for
submarine cables, but it may also be used to increase the sensitiveness of other
instruments on the moving coil principle.

page_text: 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 :
1. The improvements in telegraphic and electro-magnetic instruments of the
suspended coil type consisting in reducing the air gap of the magnet by projecting
forwards some or parts of the pole pieces to nearly touch the core of the coil and
by recessing others or other parts of the pole pieces to allow of the movement of
the coil in the recesses.
2. The improvements in telegraphic and electro-magnetic instruments substantially-
as described with reference to Fig. 1 of the drawings.
3. The improvements in telegraphic and electro-magnetic instruments substantially
as described with reference to Fig. 2 of the drawings.
4. The improvements in telegraphic and electro-magnetic instruments substantially
as described with reference to Fig. 3 of the drawings.
5. In an electrical instrument of the moving or suspended coil type a central core-
shaped with projecting edges for the purpose set forth.
6. In an electrical instrument of the suspended coil type a central coil made in.
two parts secured closely together.
Dated this 10th day of December 1896.
WHEATLEY & MACKENZIE,
40 Chancery Lane, London, W.C., Agents..