Year: 1885

page_text: I SILVANUS PHILLIPS THOMPSON of 20 Arundel Gardens Notting Hill in the
County of Middlesex Doctor of Science and Professor of Experimental Physics do
hereby declare the nature of this Invention to be as follows:-
This Invention consists of telephones constructed upon the hereinafter described
principle to serve either as transmitters or as receivers and is for the purpose of
providing compact and efficient instruments of great power. It is well known that
any dynamo-electric or magneto-electric machines will serve either as a generator
of currents or as a motor. In such machines there are usually two distinct parts
respectively called the field-magnet and the armature the relative motion of one or
both of these organs generates currents or if currents from an external source
traverse the armature mechanical motion results. And in such nachines it is usual
to make the field magnet a very powerful magnet (either permanent or temporary)
baving great magnetic inertia and the armature of small magnetic inertia and
relatively light.
My improved telephones act on the same principle as that on which dynamo-
electric machines (including magneto electric in that term) of any one of the
known types act but I make the armature or some part thereof capable of
vibration instead of the usual rotation on an axle these vibrations being com-
municated either from the armature to the listeners ear, or from the speaker's
mouth or throat to the armature by suitable mechanism or mechanisms, or simply
by the intervening air. The form of the armature may be of any of the well
known patterns such as the Gramme ring, the Siemens' drum, or other form, but
I prefer in some cases to modify the manner of grouping or connecting the coils.
The commutator common in dynamo-electric machines is no longer used; and it is
of advantage that the coils should be so grouped that they occupy the position
where the magnetic field is strongest. It is advantageous also to laminate the
cores both of the armatures and of the field magnets. When the armature is
pivotted on or about an axis a cushion or sleeve of elastic matter may be applied
at the said parts or axis When the armature or its core is mounted on a spring,
the spring may be either straight or coiled, or instead of a spring a cushion or.
mass of yielding material may be substituted. Internal magnets or electromagnets
may be placed within the armature to reinforce the magnetic field, thus enabling.
the self induction and resistance of the armature coils to be reduced.
1 L
1

page_text: I SILVANUS PHILLIPS THOMPSON of 20 Arundel Gardens Notting Hill in the
County of Middlesex Doctor of Science and Professor of Experimental Physics 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 consists of telephones hereinafter denominated Dynamo-telephones
constructed upon the hereinafter described principle to serve either as transmitters
or as receivers and is for the purpose of providing compact and efficient instruments
of great power. It is well known that any dynamo-electric or magneto-electric
machines will serve either as a generator of currents or as a motor. In such
machines there are usually two distinct parts respectively called the field magnet
and the armature the relative motion of one or both of those organs generate
currents or if currents from an external source traverse the armature mechanical
motion results. And in such machines it is usual to make the field magnet a very
powerful magnet (either permanent or temporary) having great magnetic inertia
and the armature of small magnetic inertia and relatively light.
My improved telephones act on the same principle as that on which dynamo
electric machines (including magneto electric in that term) of any one of the
known types act but I make the armature or some part thereof capable of
vibration instead of the usual rotation on an axle these vibrations being com-
municated either from the armature to the listeners ear or from the speakers
mouth or throat to the armature by suitable mechanism or mechanisms or simply
by the intervening air. Telephones constructed on this plan I call "Dynamo
Telephones The form of the armature may be any of the well known patterns
such as the Gramme ring, the Siemens drum or other form, but I prefer in some
cases to modify and simplify the manner of grouping or connecting the coils. The
commutator common in dynamo electric machines is not used in my arrangement.
It is of advantage that the coils of the armature should be so grouped that they
occupy the position where the magnetic field is strongest so that any small motion
given to them may have the greatest induction effect in transmitting or receiving
and so that any small current traversing the coils may produce the most powerful
effect in receiving the coils of the armature which may be of fine well insulated
copper wire, are connected in the line circuit. The coils on the field magnets if any
may be arranged either in a local circuit or in line or as shunt to the armature
coils. It is advantageous to laminate the cores both of the armatures and of the
field magnets. When the armature is pivoted on or about an axis a cushion or
sleeve of elastic matter may be applied at the said parts or axis. When the
armature or its core is mounted on a spring, the spring may be either straight
or coiled, or instead of a spring or cushion, a mass of yielding material may be

page_text: substituted. Internal magnets or Electro magnets may be placed within the
armature to reinforce the magnetic field, thus enabling the self-induction and
resistance of the armature coils to be reduced.
Figures 1 and 2 of the accompanying drawings shew in views at right angles to
each other, a Dynamo Telephone on the magneto principle, the armature, A, being
mounted to vibrate (on the pivot a mounted in any suitable supports) in front of
the poles of a permanent magnet B. There are two coils a, on the iron cores a³,
carried by an iron yoke a', mounted on an elastic hub a³, and suitably pivotted.
A short and light stiff connecting rod c, makes the necessary communication
between the armature and the diaphragm d. It is found desirable in setting up
the instrument to give to the armature a slight lead with respect to the field-
magnets. This has double effect, it causes any small change in position to have a
greater influence on the magnetic field, and it also gives a mechanico-magnetic
back attraction which serves to keep the diaphragm in a state of initial tension.
The diaphragm may be of mica celluloid parchment alluminium or any metal,
whether magnetic or not, its function being purely acoustic.
Figure 3 shews a ring armature, resembling that of well known Gramme
Dynamo, but having coils grouped in two sets only, connected in series, (or parallel,
if desired, for low resistance).
The ring is pivotted as before described and connected to the diaphragm as
shewn and corresponding parts to those shewn in figures 1 and 2 are marked with
the same letters of reference.
The ring may be made with protruding teeth as in the Pacinotti dynamo.
Figure 4 shews in section and figure 5 in end view a drum armature, having
central iron core-tube fixed,-a is the armature coil, as the soft iron tube, a³ ebonite
insulation, a soft rubber and a steel spindle, c is the connection to the diaphragm,
and g, support to tube, N and S, are the pole pieces. Figure 6 shews a separately
excited dynamo-telephone with local battery L, B, to excite field magnet N, S,--
In this example, the armature acts by the lever h, on the diaphragm. The parts
corresponding to those in the preceding Figures are marked with the saine letters
of reference.
Figure 7 shews diagrammatically an arrangement of two shunt wound dynamo
telephones (such as are hereinbefore described) in circuit, one as a transmitter and
the other as a receiver, a battery in line, (anywhere in the circuit) serving to excite
the field magnets, and to give the initial stress upon the diaphragms.
Figure 8 shews a way of applying a coiled spring A' to the armature A, one end
of the spring being secured to the armature, and the other end to a fixed part x,
but I prefer the use of cushions, hubs or sleeves of rubber as herein before shewn,
as metal springs, are liable to have a tone of their own.
I have described what I consider the best or some of the best means of carrying
my Invention into effect, but I do not limit myself to the precise details, which
I have described, and illustrated, as it will be evident that they can be varied
without departing from the nature of my Invention; for example, the armature
may be a soft iron piece without coils, but mounted and connected as herein before
described and in proximity to the poles of an electro-magnet or magnets.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed I declare that what
I claim is:
First. The instruments hereinbefore denominated dynamo-telephones, having an
armature, pivoted or equivalently supported in proximity to the poles of a field
magnet, and connected to a diaphragm substantially as herein before described.
Second. In a telephone, the combination of an elastically centred armature with
a field magnet substantially as bereinbefore described.
Third. In a telephone, the combination of a ring-armature or drum-armature, or
other pivotted armature, with a diaphragm, suitable for taking up the vibrations

page_text: from the armature, and imparting them to the air, or for taking them up from the
air and imparting them to the armature.
Fourth. In a telephone, the combination of a ring-armature, drum-armature, or
other pivotted armature, with a field-magnet, substantially as herein before
described.
Fifth. The several arrangements hereinbefore described and illustrated by the
several figures of the Drawings.