Improvements in Electrical Measuring and Signalling Instruments.
Year: 1894

page_text: Date of Application, 30th May, 1894
Complete Specification Left, 28th Feb., 1895-Accepted, 27th Apr., 1895
TRUVIDIONAL SPECIFICATION.
Improvements in Electrical Measuring and Signalling Instruments.
I, HERBERT WATSON SULLIVAN Electrical Engineer, of 29 Ladbroke Square,
Notting Hill London W. do hereby declare the nature of this invention to be as
follows:-
My invention relates to electro-magnetic, and other measuring and signalling
instruments.
In the case of instruments with stationary magnets, I may use a device, whereby
the instrument is made to serve a double purpose.
To this end, I employ two magnets, preferably semi-circular in shape, & two coil
systems.
°
The magnets are so placed in relation to each other, that they form two inde-
pendent & oppositely directed fields, the north pole of No. 1, & the south pole
of No. 2, enclosing one field, & the south pole of No. 1, & the north pole of No. 2,
similarly enclosing the other, with an independent coil system working in each.
may so lead the current to & from the coil, or coils that fixed connections to the
same are dispensed with. With this object, I suspend the coil system, by means of
a torsional wire above & beneath it, between the two arms of a suspension frame,
which may be slid on or off, a fixed upright pillar, fitted with a keyed way. Upon
the lower arm of this suspension frame, I fix two insulated contact studs, which are
in electrical connection through the suspension wires & frame, with the coil system.
Now, when the frame is pushed down into its position between the magnet poles,
the contact studs press against two insulated springs in connection with the
terminals of the instrument.
1 sometimes use an arrangement (other than that, as described in the Specification
of Letters Patent, No. 238 of 1893, granted to me) for varying the deflecting
moment (& by necessary consequence) the periodic time of the instrument. The
arrangement may adopt to this end, is that of moving the magnet or magnets in
such direction that the intensity of the field or fields, in which the coil or coils
work, is altered.
In order to balance the coil system, so that the centre of gravity shall always be
at the axis of rotation, I may employ the radial arm device, as described in the
Specification of Letters Patent No. 238, of 1893 granted to me, but in certain
cases, I attach the aforesaid radial arm to any part of the back or front of the coil
system, instead of only to the top centre, as described in the aforesaid
Specification.
Sometimes I find it convenient to make the magnets adjustable in any required
direction in order that when no current is passing, & no torsion is given to the
suspension wires of the coil system, the plane of the latter is exactly parallel to the
lines of force.
Electro-magnetic & mechanical vibrations, I may remedy as follows:-I make
rigid those parts of the suspension wire which immediately adjoin the coil, or coils,
& pass each rigid part through a bearing attached to or independent of the pillar
supporting the coil system, as described in the Specification of Letters Patent,
No. 238, of 1893, granted to me. One rigid part, or both, I lightly envelope or
partially surround with one or more folds of some very soft & yielding woven
fabric, such as velvet, velveteen plush & the like. In place of the woven fabric,

page_text: I may use a bush or bundle of fine fibre, for instance fibre, such as is known
generally to artists as camel's hair. If the coil system be suspended by wire or
other torsional material, the fabric, or bush, or bundle may embrace the material
itself, as well as the rigid piece, or both, either in part or for their entire length.
In certain cases, I may dispense with the through bearings.
This improvement I may also apply to any other forin of instrument working
with a suspended system.
Dated this 29th day of May 1894
Improvements in Electrical Measuring and Signalling Instruments.
HERBERT WATSON SULLIVAN 29 Ladbroke Square, London, W. Electrical
Engineer, 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 electro-magnetic & other measuring & signalling
instruments.
(1) In the case of instruments with stationary magnets, 1 may use a device,
whereby the instrument is made to serve a double purpose. To this end, I employ
two magnets, preferably semi-circular in shape, & two coil systems. The magnets
are so placed in relation to each other that they form two independent & oppositely
directed fields, the north pole of No. 1 & the south pole of No. 2 enclosing one
field, whilst the south pole of No. 1 & the north pole of No. 2 similarly enclose the
other field, with an independent coil system working in each. See Fig. 1, in which
the magnets (M) & (M¹) & the coils (C) & (C) are shown in plan.
This arrange-
ment affords all the advantages of two independent instruments in one.
(2) 1 may so lead the current to and from the coil or coils that fixed connections
to the same from the galvanometer or instrument terminals are dispensed with.
With this object I suspend the coil system by means of a torsional wire above and
beneath it, between the two arms of a metallic suspension frame which can be slid
on and off fixed or movable upright pillar, fitted with a keyed way or other
device for centralising the coil between the magnet poles. The lower arm of this
suspension frame is of insulating material, preferably ebonite, and bears projecting
from its lower face two insulated contact studs which are in permanent electrical
connection through the frame and suspension wires with the coil system, and so
placed that when the frame is pushed down into its position between the magnet
poles, they press upon two insulated springs fixed in the base of the instrument.
and in permanent connection with the terminals. Figs. 2 & 3 show the arrange-
ment in elevation. (UP) is the upright pillar, keyed or otherwise; (t) a tube
fixed to the suspension frame and large enough in diameter to slide over (U P);
(cs) & (cs) are the contact studs, and (s) & (s') the contact springs. It will be
seen that the object of making the lower arm of the suspension frame of ebonite is
to avoid shortcircuiting the coil where wire suspensions are employed.
(3) I sometimes use an arrangement other than that as described in the Specifica-
tion of Letters Patent No. 238 of 1893 granted to me, for varying the deflecting
moment and by necessary consequence the periodic time of the instrument. The
arrangement I may adopt to this end is that of moving the magnet or magnets in
such direction that the intensity of the field or fields in which the coil or coils work
is altered. Fig. (4) gives a side view of my way of accomplishing this object.
(M) is the magnet, (BH) a brass head or handle fixed to the back of (M). Thus
by pushing or pulling (BH) the position of the gap between the poles is varied in
relation to the coil.

page_text: (4) Sometimes I find it convenient to make the magnet or magnets adjustable in
any required direction in order that when no current is passing and the suspension
wires have no twist imparted to them, the plane of the coil or coils shall be exactly
parallel to the lines of force. Theoretically, a coil of diamagnetic wire should
always when idle, hang thus truly in the field of force. As is well known,
however, even coils of copper wire wound in the ordinary way, frequently show
slight traces of polarity by reason of minute impurities in either the wire itself, or
its insulating covering, or in both, but chiefly the first mentioned. If the magnet be
pierced and held to the base by screws, subsequent adjustment is impossible, whilst
the instrument may be found to give a greater deflection with a given strength of
current upon one side of zero than upon the other side. This defect I obviate by
clamping the magnet in position, so that by loosening the clamp or clamps it may
be turned or adjusted axially, as occasion may require. Figs. (5) & (6) show the
arrangement in plan and section. (M) = the magnet; (M C) & (M C') the
magnet clamps, and (MP) & (M P') pillars on to which (M C) & (M C¹) screw.
(5) Electromagnetic and mechanical vibrations I may alike remedy as follows:-
I make rigid those parts of the suspension wires which immediately adjoin the coil
or coils, and pass each rigid part through a pierced bearing or aperture, attached
to, or independent of, the pillar supporting the coil system, as described in the
Specification of Letters Patent No. 238 of 1893 granted to me (with only this
difference viz. that the rigid part may at no time touch the pierced bearing or
aperture). One rigid part or both I lightly envelop or partially surround with one
or more folds of some very soft and yielding woven fabric, such as velvet, velveteen,
plush and the like see Fig. 7. (cp) is a light wooden clamp fixed to the pillar of
the suspension frame and lined opposite the suspension wire (w) with velvet (v) & (v1).
The pressure of (v) & (v) upon (w) is regulated by turning the adjusting
screw (As) according to the degree of damping effect required. In place of the
woven fabric I may use a bush or bundle of fine fibre, such for instance, as is
known generally to artists as camel's hair, but whether the coil be suspended by
wire or other material, the fabric or bush or bundle may embrace the material
itself as well as the rigid piece, or both, either in part or for their entire length.
Figs. (3 & 8) shows the latter arrangement. The holder of the brush (CB) fits
into a hole pierced preferably in the upright pillar of the suspension frame, and is
adjustable forward and backward in this hole by any suitable means.
Thus on
advancing or receding the brush it is made to cover more or less closely that part
of the suspension immediately facing it. This improvement I may also apply to
any other form of instrument working with a fine suspension, whether or not
provided with the pierced bearings or apertures as explained.
Having thus particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed and carried into effect,
I declare that what I claim is :-
(1) In any moving coil instrument the use of two magnets and two coils so as to
form two independent instruments, as described in paragraph (1) and shown in
Fig. 1.
(2) In any moving coil instrument an automatic contact making suspension
frame, whereby fixed connections between the coil and the terminals are dispensed
with, as described in paragraph (2) and shown in Figs. 2 & 3.
(3) In any moving coil instrument a device for varying sensibility and periodicity.
by altering the position of the magnet in relation to the coil, as described in
paragraph (3) and shown in Fig. 4.
(4) In any moving coil instrument a clamping arrangement which allows of the
magnet being adjusted, axially, as described in paragraph (4) and illustrated in
Figs. 5 & 6.
(5) In any moving coil instrument simple damping arrangements as described in
paragraph (5) and illustrated in Fig. 7 and Figs. 3 & 8.

page_text: (6) An instrument of the moving coil type substantially as described and
illustrated.
(7) In an instrument of any type with moving parts simple damping
arrangements as described in paragraph (5) and shown in Fig. 7 & Figs. 3 & 8.
Dated this 27th day of February 1895.
H. W. SULLIVAN.