Improvements in and connected with Electrodynamometers.
Year: 1899

page_text: Communicated from abroad by ALLGEMEINE ELEKTRICITATS GESELLSCHAFT, of
Schiffbauerdamm 22, Berlin, Germany.
Improvements in and connected with Electrodynamometers.
I, VICTOR ISIDORE FEENY, of 60, Queen Victoria Street, in the City and County
of London, E.C., Chartered Patent Agent, 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 relates to improvements in and connected with electrodynamo-
meters, and has for its object the provision of an efficient damping device there-
for.
Now in the dynamometric measuring instruments hitherto introduced, it is
not possible to effect a suitable magnetic damping, since the damping magnet
loses its continuous magnetism under the influence of an alternating-current field.
In the present invention, the magnetic field of the dynamometer is so circuited
that it cannot affect the damping magnet and, consequently, cannot impair it.
This is effected by embedding the fixed coil F of the dynamometer in an iron
body E, in the manner illustrated in the diagrammatic Figures 1 and 2 of the
annexed drawing. This iron body receives the lines of force of the alternating
current field of the dynamometer coils and determines their course as indicated
by the broken lines in Figure 1, whilst the interior of the coils remains free from
the presence of iron, which fact is of great importance in regard to proper self-
induction.
In this manner, the path of the lines of force outside the effective or inner
part of the coil is so prescribed, that no magnetic leakage of any consequence is
possible, and the damping magnets D which act in the sense of damping upon a
inetal disc or fan A connected with the shaft, can be located or arranged quite
near thereto.
The damping magnets are, in this way, removed from the danger of losing
their continuous magnetism under the influence of the alternating-current field.
Figure 1 of the annexed drawings is a plan view and Figure 2 a side elevation
of the same, both being diagrammatic.
Figures 3 and 4 are a side elevation and a plan respectively, being detailed
views of an electrodynamometer, with magnetic damping constructed in accord-
ance with this invention.
The magnetic field of the dynamometer is formed so that it does not act on
the damping magnet, and that in consequence, it cannot injuriously affect it,
in the following manner. In a wood casing is secured to a suitable bed-plate an
iron body formed of plates of sheet iron having an oval centre or bore. In the
centre is situated the fixed coil of the dynamometer through the middle of
which passes the spindle a on which the rotary coil of the dynamometer as
well as the pointer Z and the spiral springs G are arranged. If current
passes through the fixed coil F and the movable coil, the latter is caused to
revolve in the usual manner, and this motion is resisted by the springs, and the

page_text: pointer brought to rest over the scale S which is graduated in accordance with
experience.
On the spindle, beneath the rotary coil is an aluminium disc A which oscil-
lates or moves between the poles of the two permanent magnets D D so that the
oscillation of the pointer is damped. The supply of current to the fixed coil is
effected through the terminals K, and to the movable coil through the terminals N.
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:
A dynamometer with means for magnetic damping, in which the fixed coil
is so embedded in an iron. body that the magnetic lines of force, of the alter-
nating current, thereby produced, outside the effective inner part of the coil, so
run that the damping magnets cannot be injuriously affected, whilst the interior
of the coils remains free from the presence of iron, substantially as described.
Dated this 29th day of December 1899.
For the Applicant,
GEDGE & FEENY,
Chartered Patent Agents, 60, Queen Victoria Street, London, E.C.