Improvements in Electric Meters.
Year: 1892

page_text: Date of Application, 4th Mar., 1892
Complete Specification Left, 3rd Dec., 1892-Accepted, 7th Jan., 1893
Improvements in Electric Meters.
I, ROBERT WILLIAM PAUL of 44, Hatton Garden, E.C. in the County of
London, and Frith Knowl, Elstree in the County of Hertfordshire, Electrician
and Scientific Instrument Maker, do hereby declare the nature of this invention to
be as follows:-
My invention relates to improvements in galvanometers whereby their use is
rendered more convenient and expeditions.
For the purpose of the invention I construct a galvanometer with suspended coil
moving between the poles of a magnet as in the type of galvanometer commonly
called the D'Arsonval; the coil being preferably suspended by a flat strip of
phosphor bronze through which the current passes into the coil, leaving it by a
spiral below after the manner recently published. But to render the instrument
more portable, and the moving parts self-contained I enclose the coil in a tube,
preferably of silver so as to act as an efficient damper of vibrations; at one end of
the tube is an attachment for carrying the mirror or other index, and the suspending
strip, while the other end is provided with an insulated pin through which the
current may pass to the spiral below.
The tube, suspending strip and spiral are enclosed in an outer tube or case
provided with an aperture, preferably glazed, opposite the mirror, and carrying the
adjusting head with suspending strip attached above, and an insulated pin or screw
below to which the lower end of the spiral is attached. To enable the instrument
to be readily moved without damage to the moving parts I clamp the coil by means
of the silver tube containing it, (which may be cut away in certain places for
lightness,) by means of the following device or its equivalent. A spring attached
to the outer tube or case is arranged to press on the silver tube through an aperture
in the former, or it may act ou a stud or pin which passes through a hole in the
outer tube to clamp the coil, but may be withdrawn and held back by sliding it in a
slot or otherwise when the coil is to hang free. The outer outer tube or case may be
slid into a socket in the base of the instrument so that the coil is between the poles
of a powerful magnet which I prefer to make in the form of a circular ring of
rectangular section with a narrow air-gap. The base, which may be of brass carries
levelling screws, which may be provided with ebonite fect to give good earth
insulation, and also the terminals, one of which must be insulated from it.
Dated this 4th day of March 180°
ROBT. W. PAUL.
COMPLETE SPECIFICATION.
Improvements in Electric Meters.
1, ROBERT WILLIAM PAUL, Electrician and Manufacturer of Scientific
Instruments, of 44 Hatton Garden and Leather Lane in the County of London
and of 33 Regent Square in the County of London, and of Frith Know! Elstree
in the County of Hertfordshire 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 :-
My invention relates to the class of instruments for the measurement of electric
currents known by the name of d'Arsonval and consists of a coil of wire through
which the current to be measured passes, suspended in a magnetic field in such a
manner as to turn in opposition to the torsional rigidity of the suspension on the
Primer

page_text: passage of a current; the motion of the coil may be observed either by the reflecting
method or by a pointer moving over a divided scale. But in order to make the
instrument dead beat or aperiodic and to enable the coil to be suspended and
clamped without fear of injury I place it in a light tube of silver or other good
conductor and suspend the coil by means of attachments to the tube.
The coil is wound in the manner already published as that having the greatest
suitability for the purpose, its cross section being in the form of two tangent circles,
and its length being great in proportion to its width.
In order to prevent the risk of injury to the coil and its containing tube I prefer
to enclose them in a metal case provided in the case of reflecting instruments with
a sliding glass window and also a torsion head for directing the angular position of
the coil, and means for clamping the coil tube and for leading the current into the
coil. This case I usually mount in a base which may be of metal and provided
with levelling screws, insulated terminals connected to the coil and a strong
permanent magnet between whose poles the coil is suspended; a level may be also
provided.
Referring now to the accompanying drawings for the purpose of more clearly
explaining my invention and the manner in which it may be carried into effect:
Fig. 1 is a part elevation and part section of an instrument containing the
improvements referred to above.
Fig. 2 is a part plan of the same, the instrument being nearly symmetrical about
the line X Z.
Fig. 3 is a back view of the coil-tube and mirror and
Fig. 4 a front view of the coil.
A is a base plate which may be of cast brass and provided with three bosses
underneath in which the levelling screws B are tapped the screws B are provided
with ebonite feet at the lower ends so as to insulate the instrument from anything
upon which it stands, the magnet C which has a narrow gap between the poles and
is held down to the base by the plate D in which is rivetted the boss F, the plate D
being bolted onto the base A by the bolt G and nut H and provided with a circular
level E screwed to its upper surface. The magnet is prevented from moving
sideways on the base A by the three screws K. tapped into the base A. The tube N
is shouldered down at one end and soldered into the base A and holds the case
containing the coil etc. This case is formed of the tube O which is shouldered down
at the upper end and passes through the plate P where its end is spun over and
soldered; a second plate P forms with the first and with the tube Q a chamber
nearly circular in form but cut away in front where it is closed by a glass plate S
which slides in dovetail grooves in the plate P; the upper plate P carries the tube R
fixed to it and in the upper end of the tube R is fitted the torsion head consisting
of the milled bead T which is fixed to the short tube V which latter turns in the
tube R the head T is drilled partly with a large hole and partly with a small one
and through them passes the suspension strip a of phosphor-bronze of small section
the strip a being soldered on the top of the lead T and the soldered joint is covered
by a cap w fitting onto the head t the lower end of the strip a is soldered to the
tang, attached to the plug e in the ends of the light silver tube f. The piece b
has the mirror attached to it by means of a 3 armed metal clip c.
The lower end
of the coil tube has a plug n through which passes the pin h. which is insulated
from it by the ebonite bush m. screwed into the plug n and the pin his fastened by
the nuts 1. 1. on each side. One end of the coily passes through the wall of the
tube and is soldered to it at the other is soldered to the pin h, to the lower end
of which is attached the spiral O, the other end of the spiral is soldered to the
screwed pin p. fixed in the ebonite collar by means of the mut, the pin p has a
hexagonal head so made as to prevent it turning in the collar . when the nutris
tightened. Connection is made from the screw to the insulated terminal L by
means of the flat spring M which is slotted so as to allow the pin p to pass through
and to be clamped to it by the milled nut 1. To clamp the coil for travelling I
provide the flat spring which is screwed to the under side of the plate P. by the

page_text: screws and hangs down in front of the tube O, a slot is made in the lower end of
the spring in which a plug y works up and down being held by the nut ; in the
position shewn it allows the coil to swing free but when pushed up the slot till
opposite the hole i it drops through and holds the coil tube in place by pressure
of the spring x. The second terminal is fixed directly onto base and connection
from it to the outer end of the coil is made through the case O. Q. R and the
suspending strip a.
The methods of protecting, suspending, damping enclosing or clamping the coil
of an instrument of this type may be applied to instruments with pointers in place
of mirrors and the clamping device and case may be used for instruments in which
the coil is not enclosed in a protecting and damping tube like that described.
Having now particularly ascertained & described the nature of my said inven-
tion and in what manner the same is to be performed 1 declare that what I
claim is :-
1. In electric meters consisting essentially of a coil moving in a magnetic field the
enclosing of the coil in a tube for the purpose of either damping its motion of
suspending it without straining it or of protecting it or for any or all of these
purposes.
2. In electric meters the device for clamping the coil in place for travelling or to
throw the instrument out of action substantially as described.
3. In electric meters the method of connecting the coil to the terminals by means
shewn in Fig. 1 at p q r m, or their equivalent, so as to allow the working parts to
be examined and connected in circuit by placing them in position or so as to allow
two or more coils to be used in the same instrument.
4. The improved electric meter substantially as described.
Dated this 3rd day of December 1892.