IMPROVEMENTS IN ELECTRIC AND MAGNETIC APPARATUS FOR TELEPHONIC OR OTHER PURPOSES
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by Silvanus Phillips Thompson and José
Dottin Husbands at the Office of the Commissioners of Patents on the
1st December 1882.
SILVANUS PHILLIPS THOMPSON, of University College, Bristol, Professor of
Experimental Physics, and JosÉ DOTTIN HUSBANDS, of Queen Victoria Street, in
the City of London, Gentleman, IMPROVEMENTS IN ELECTRIC AND MAGNETIC
APPARATUS FOR TELEPHONIC OR OTHER PURPOSES "
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Our invention relates to electric and magnetic apparatus and is applicable for
telephonic and various other purposes.
Our said invention consists in utilizing, as means for producing mechanical
movements, the property of differential magnetic expansion and contraction, that
is to say, the action due to the different degree or amount of expansion or
contraction of different metals when magnetized or acted on by magnetic forces.
There are some metals, for example, iron, steel and cobalt, which, when magnetized,
expand or elongate in the direction of the magnetizing force. There are others
(for instance nickel) which contract when magnetized, and there are other metals,
such as, brass, silver, zinc or tin and other hard bodies, such as, ivory, horn, wood or
glass, which, when subjected to magnetic forces, are indifferent, that is to say, they do
not become magnetized and neither expand nor contract. Now we find that, if, in
any apparatus, instrument, device or structure, pieces or parts formed of such metals
are so combined that, when subjected to a magnetizing force, some part of the
structure is thereby caused to elongate whilst some other part is caused to contract,
movements or displacements ensue, which, if properly utilized or turned to account,
may be caused to impart motion with greater effect than could be obtained by the
mere expansion or contraction of any single metal. Thus, for example, if a compound
strip be formed by rivetting, soldering or otherwise firmly and intimately attaching
a thin piece of iron to a thin piece of a substance which, when magnetized, does not
expand, or which expands less than iron, or which contracts; then such a compound
strip, when magnetized, exhibits a tendency to curl or bend, the elongating metal
curling around within or beside the other substance of the said compound strip.
It is practicable to construct, on this principle of "differential magnetic, ex-
pansibility," springs, screws, spirals, tongues, coils, levers, discs, chains, arches,

page_text: diaphragms, tubes, or other parts or objects which may be utilized in or applied to,
or used in connection with, magnetic and electric instruments or apparatus for various
purposes.
In some telephonic instruments we utilize this principle of differential magnetic
expansion and contraction by forming a strip or piece of iron and nickel or like
metal, soldered or otherwise closely or intimately united. We attach one end of
this strip to the diaphragm or tympanum and the other end to the case of the
instrument in such a manner that the tension upon the said strip or piece can be
adjusted by a screw or other suitable means. This strip or piece is either enclosed
in an ordinary coil or an insulated copper wire is wound around the same to form
the coil, which is included in the.telephonic circuit.
We sometimes so construct the instrument that the vibrations of the disc or
diaphragm are caused by the expansion and contraction of strips or pieces of
different metals, such as, iron and nickel, attached to the diso or diaphragm, which
pieces are made with extensions passing through coils included in the telephonic
circuit.
In some instances we utilize the varying attractive power of pieces of magnetic
metal enclosed within a coil included in the circuit. For this purpose we construct
the instrument as follows, that is to say:-According to one form.or modification
we employ a series or number of rings or links of iron having a piece cut out of
one side and an insulated wire coiled around them, so that, on the passage of the
current, they will be magnetized and their two ends or poles attracting one another
will cause the said rings or links to contract. These rings or links are connected in
any suitable manner, the link at one end of the series is connected to the disc or
diaphragm or to a strip, reed or tongue projecting therefrom, and the link at the
other end of the said series is connected to the case of the instrument, so that any
variation in the current flowing through the said wire will cause a corresponding
expansion or contraction of the said links or rings and thus produce vibrations of
the disc or diaphragm. The coils around the said rings may be arranged either in
series or in derived circuits.
According to another modification of our invention we form each of these links
in three pieces two of which are of iron and connected to the third piece by pieces
of brass or other semi-magnetic or non-magnetic metal.
In some instances we utilize the combined actions of magnetic attraction, and
expansion and contraction of metal, for imparting the vibrations to the disc or
diaphragm, the instrument in this case may be constructed in numerous forms or
modifications some of which are hereinafter described by way of example.
According to one form or modification we employ a wire, strip or piece of nickel
or other metal which contracts under the influence of an electric current passing
through a coil of insulated wire, this wire, strip or piece is connected at one end to
the disc or diaphragm or to a bar, reed or tongue projecting therefrom, and at the
other end to the case of the instrument where it is provided with an adjusting
screw and we fix on or secure to it in any suitable manner a number of pieces of
iron. The said wire, strip or piece may be straight or of spiral or other convenient
form and is suitably arranged within the coil which is included in the telephonic
circuit, so that, when a varying or pulsating current is passing through the said
circuit, the said wire, strip or piece contracts or expands under the influence of
such current and of the varying magnetic attraction between the pieces of iron.
According to another form or modification we employ a number of wires, strips
or pieces of nickel or other metal connected by means of iron bolts and nuts which
are magnetized and attract each other when the current is traversing the coil.
Another modification consists in forming the pieces of iron (which may be either
solid or tubular) with internal or external screw-threads and screwing them into or
upon a spiral wire of nickel or similar metal.
In some cases, we arrange springs between the pieces of iron, and, in other cases,
we bend the wire, strip or piece of nickel or other metal between the pieces of iron
to increase the elasticity of the said strip or piece.

page_text: In another form of our invention, we modify the same by the loose combination
of pieces of different metal one contractive and the other expansive under the
influence of an electric current passing around the same; one of these metal pieces
is fastened to a diaphragm, disc or sounding board and the other metal piece to the
case. These two pieces are held together in any elastic manner; we prefer that
each piece should be half round so that when fitted together the two pieces form a
round piece or bar on which we form a screw thread, and the two pieces are held
together with their flat surfaces in loose contact by means of a spiral wire coil
which fits the screw-thread and serves as a nut.
In other cases, we coil a wire of magnetic metal upon a bobbin and arrange the
same so that some of the turns of the said wire are in contact with the disc or
diaphragm, or with a split hoop or ring surrounding the coil and connected to the
disc of diaphragm.