IMPROVEMENTS IN MAGNETS
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by Joseph Sinclair Fairfax at the Office.
of the Commissioners of Patents on the 10th July 1882.
JOSEPH SINCLAIR FAIRFAX of Westminster in the County of Middlesex,
Consulting Engineer 'IMPROVEMENTS IN MAGNETS"
Es
This invention relates to a novel construction of permanent and electro magnets,
whereby greater efficiency and more convenient forms may be obtained.
It is a well known fact that permanent and electro magnets have been constructed
of thin plates which have been found to be more powerful than solid ones of equal
weight used under similar conditions. This result appears to arise from the
magnetic inertia being greater in the solid mass; or that the thin plates afford a
greater opportunity for the flow of the current to take place upon parallel lines,
there being fewer cross currents; and that the molecules composing the magnet are
more readily polarised or disposed symmetrically along the lines of force.
It is also well known that when iron filings are sprinkled upon paper, and either
subjected to the influence of a powerful magnet, or an electric current, the particles
arrange themselves upon the lines of magnetic force, although the resistance to their
doing so, offered by friction and gravitation, is very considerable.
Now by this invention magnets may be wholly or partially constructed of filings
or other small pieces of metal, divided in any suitable way, and arranged in any
suitable form, and the said particles may be either placed within a case or shell, or
if an electro magnet, within a coil of wire; and if more convenient, combined with
solid bars, plates, wires, pole pieces, or keepers as required; and used for any
purpose for which a magnet is applicable.
In filling the magnet case or shell with the said particles, a current of electricity
may be sent through the same, thus causing the filings to be arranged according to
their greatest polarity, and therefore more readily magnetised or demagnetised; and
the electric current and wires may be so conducted as to produce both north and
south poles within the same transverse area of the magnet. The particles may be
subjected to motion or percussion during the process of forming the magnet; in
order to assist the polar arrangement of the same, and then compressed and held
by suitable fastenings; so that magnets of great efficiency and variety of form may
thus be made.

page_text: In constructing magnets for dynamo machines it is desirable to produce as large
and as powerful a field of force as possible, but in winding the magnet coils the
outer layers of wires which conduct the current have less relative efficiency than
those next to the core; and there are obvious practical difficulties involved in so
forming the solid core as to avoid this drawback By this invention the wire may
be arranged in any convenient manner and the interstices filled up by filings or
finely powdered iron, and securely bound together as before stated; thus distri-
buting the current equally throughout the mass, with the minimum amount of wire,
weight, and space.
As the cost of making such small particles as filings especially for the purposes
of this invention would necessarily be great, I prefer in some cases to take the
ordinary turnings, borings, shavings, or chips made by machine tools in reducing
iron and steel to size or form, and to pulverize them to a powder, which may then be
sifted for the degree of fineness required. As there are frequently hard portions in
iron and steel, and it being desirable to have a perfectly homogeneous material for
this purpose, I prefer to heat and properly anneal the metal used; either before
or after pulverizing, as may be found most desirable, and then proceeding as before
stated.