Improvements in and relating to the Deprez-D'Arsonval Galvanometer.
Year: 1893

page_text: Date of Application, 5th Jan., 1893
Complete Specification Left, 3rd Oct., 1893-Accepted, 5th Jan., 1894
PROVISIONAL SPECIFICATION.
Improvements in and relating to the Deprez-D'Arsonval
Galvanometer.
HERBERT WATSON SULLIVAN 29 Ladbroke Square Notting Hill London W.
Electrical Engineer, do hereby declare the nature of this invention to be as
follows:-
This invention consists of improvements of the instrument known generally as
the Deprez-D'Arsonval galvanometer (Ayrton Mather type).
In place of a single magnet, two or more magnets are used, with their like poles
joined by pole-pieces, & the coil, which may be single or compound, swings in the
focus of the strong magnetic field thus produced.
The magnets are tapered at their ends to fit against, or into, their respective
pole pieces, & arrangements are. provided for varying, at will, the deflecting
moment of the instrument, with a given strength of current.
This galvanometer has a higher figure of merit than any existing D'Arsonval
galvanometer, for the same coil resistance, & it would be very useful on board
ship, devices being adopted to eliminate disturbing oscillations due to the rolling
& pitching movement of the vessel.
Dated this 5th day of January 1893
H. W. SULLIVAN.
COMPLETE SPECIFICATION.
Improvements in and relating to the Deprez-D'Arsonval
Galvanometer.
I, HERBERT WATSON SULLIVAN, 29 Ladbroke Square, Notting Hill,
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 consists of improvements in, and relating to, the instrument known
generally as the Deprez-D'Arsonval galvanometer (more particularly of the
Ayrton-Mather type), the objects being to obtain (1) a more concentrated field of
magnetic force, and consequently greater deflecting moment. (2) An instrument
of which the deflecting moment, with a given strength of current, can be varied at
will. (3) An instrument to be as serviceable on board ship as on shore..
(1) In place of a single magnet, compound or otherwise, and preferably
C shaped, I may use two similar magnets, placed either horizontally or
vertically to, and facing each other, with their poles D & C Fig. 1, in unison, and
in as perfect contact as is possible. The poles of each magnet are tapered from
the centre to the ends, and are fitted with or without pole pieces, against each
other as at Fig. 1.
Alternatively, I may use an inner and an outer magnet or magnets, similarly
connected, as shown E. H & I Fig. 2. Or, I have one or more auxiliary magnets,
with their like poles grafted into those of the main magnet as at M Fig. 3.
(2) With the existing forms of Deprez-D'Arson val galvanometer, the deflecting
moment can be varied alone by the (in many cases) inconvenient method of
partially short-circuiting the poles.

page_text: The method I adopt is that of altering the position of the coil S. Fig. 4 in the
magnetic field, either horizontally, or vertically, or diagonally, or in any other
direction, by means of a screw and ratchet arrangement fixed on the base and
workable without removing the cover of the instrument, or by some similar device,
as shown in Fig. 4.
The plate a is fixed to the base of the instrument, the plate bis moveable
between slides. The screw d is loose in the bearing & and screws in the bearing y.
Thus when dis turned it will cause to move horizontally backwards or forwards.
On plate bis fixed the pillar e which carries the coil S so that by turning screw d,
coil S can be moved backwards and forwards in the magnetic field.
fixed to the pillar e, and his another tube sliding in it. To the coil S is fixed
by its suspension, so that by sliding h up and down in p, S can be moved vertically.
S can be moved diagonally by rotating the tube / in tube p.
is a tube
(3) The Deprez-D'Arsonval galvanometer of the existing forms is unsuited for
use on shipboard by reason of the coil oscillations set up by the rolling and
pitching motion of the vessel. Such oscillations may be, and usually are, of a two
fold character. (1) Those due to the circumstance of the centre of gravity not
being in line with the coil and its suspensions. (2) Those produced by the weight
of the coil causing it to sway, more or less, from out of the straight line, with
each inclination of the ship from the horizontal plane, so that an imaginary line
drawn between the points of suspension would not pass through the centre of the
coil. Moreover the repeated stress to which the suspension is thus subjected, has
a tendency to "tire" and eventually break it. The heavier the coil, and the
lighter the suspension, the more marked do these objections become.
shall hereinafter refer to as the "want of balance," and effect (2) as the "sag."
Effect (1) I
Obviously, both effects can be partly eliminated by the use of a gimballed table,
but this has been found not to respond rapidly enough to sudden movements of the
ship and to be inconvenient practically..
(4) To compensate for the "want of balance," I fix to the top centre of my coil
by suitable means, and projecting from it in the required direction, either
horizontally or at an angle, one or more radial arms of light non-metallic substance,
preferably shellac, sealing-wax and the like compounds. Also, I may substitute
for any one of these some light, non-oxydisable and dia-magnetic metal,
e.g. aluminium brass and the like (a Fig. 5 represents one of these arms fixed to
coil S). The advantage of this device is in that it enables the coil to be readily
balanced with the least possible addition to its weight.
(5) To remedy "sag," I make rigid those parts of the suspension immediately
adjoining the coil, and pass each rigid part through a bearing attached to, or
independent of, the pillar supporting the coil system. When the ship heels over, the
bearings take the weight of the coil, thus keeping it practically within the straight
line, and preventing all injurious strain on the suspension. (In Fig. 6 R and r are
the rigid parts fixed to the coil S, and B and bare the bearings). N.B. These
rigid parts may be so adjusted with relation to the bearings that in case of breakage
of the suspension, the bearings support the coil and prevent it from falling out and
sustaining damage. Alternatively, and with the view of lessening friction between
the rigid parts and bearings at times of motion, I employ only one rigid part (R
Fig. 7) one bearing (B Fig. 7); and two coils (S & S Fig. 7) of equal size and
weight suspended in the same system. The one coil is immediately above the other,
but separated from it by the rigid part, and the two are so connected in the circuit
as to be similarly influenced. The bearing must embrace the rigid part at a 5
position, approximately equi-distant between the two points of suspension. In the case
of galvanometers having hollow cores, I use also but one rigid part, this working in
a central bearing inside the core and its surrounding coil. Preferably, I pass the
fixed arm or support carrying the bearing, through an aperture pierced in the core
midway between its ends and at right angles to the plane of the coil. The rigid 5
part is suitably fixed inside, and to the coil, in a line between the two points of
suspension. Such rigid part, may or may not be the entire inner length of the

page_text: The
coil. In Fig. 8 C is the core shown in section and viewed from the front. C, is
the core shown in section and viewed from the side, R is the rigid part fixed to the
coil S. The coil S is shown at S, in section and viewed from the side.
bearing B forms part of the arm d by which the core C is fixed to its supporting
pillar p.
The fixed arm or support carrying the bearing, and which must be of
some dia-magnetic metal, I sometimes extend through a corresponding aperture on
the opposite side of the core, and provide with an adjustment for exactly centralising
the bearing in relation to the rigid part. In Fig. 9 n is a screw and 6 is the bearing
sliding through the core cat y. The screw n screws in the core at r and is loose
in a socket on the bearing b at 2. When the screw n is turned it will push the
bearing b backwards or forwards so centralising the bearing b in relation to the
rigid part. I wish it to be understood that I may interchange the positions of
the bearing and rigid part.
r
"
(6) Another plan, I sometimes employ, either with or without the above
mentioned device, to prevent sag is by means of an automatic "governor
arrangement (see Fig. 10). (S. S,) are the top and bottom springs of the
suspended coil system. Above (S,) I place a rocking arm or disc (d) on each side
of which and resting lightly upon it, I provide two levers (l. l,) pivoted at the
points (Z. Z) and extended to points (m. m). In a direct line below (S,) but not
connected with it, I hang a "plumb bob " (p, b). The action of this arrangement
is such that when the ship rolls or pitches then according to the direction in which
the instrument points (p. b) is carried over towards (m) or-(m,) against which, if
the motion of the ship suffice, it strikes, causing the lever of the corresponding side
to press on the rocking arm or disc (d) and so compress spring (S). Mechanical
stops are provided to prevent over compression, and consequent danger of breaking
the suspension.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. In any galvanometer of the Deprez-D'Arsonval form the use of two or more
magnets with like poles joined by pole pieces or otherwise, as described in
paragraph 1 and shown in Figures 1, 2 & 3.
2. In any galvanometer of the Deprez-D'Arsonval form the use of a screw and
ratchet arrangement, or similar device for varying at will the position of the coil in
the magnetic field, as described in paragraph 2 and shown in Fig. 4.
3. In any galvanometer of the Deprez-D'Arsonval form the use of a coil
balanced substantially as described in paragraph 4 and illustrated in Fig. 5.
4. In any galvanometer of the Deprez-D'Arsonval form the employment of a coil
system with rigid part or parts, working in a bearing or bearings, in order to
prevent sag," substantially as described in paragraph 5 and illustrated in
Figures 6, 7, 8 & 9.
66
5. In any galvanometer of the Deprez-D'Arsonval form the use of an automatic
"governor" arrangement in order to prevent "sag," as described in paragraph 6
and illustrated in Fig. 10.
6. An instrument of the Deprez-D'Arsonval form, substantially as described and
illustrated.
Dated this Third day of October 1893.
ELLIOTT BROTHERS,
Agents for H. W. Sullivan.