Improvements in Magnetic Compasses.
Year: 1891

page_text: Date of Application, 18th July, 1891-Accepted, 22nd Aug., 1891
COMPLETE SPECIFICATION.
Improvements in Magnetic Compasses.
I PIETER JAN KAISER of Noordeinde No. 52 Leiden in the Kingdom of
Holland Adviseur-Verificateur of the Nautical Instruments of the Dutch Navy
(Royal) 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 :-
The desire has long been entertained to possess a compass with a floating card
which shall combine lightness with great magnetic force, as experiments in that
direction have proved that a card of light weight is but little if at all liable to
disturbance arising from the vicinity of iron in ships, whilst it was also found that
such disturbance could also be materially reduced by the use of card magnets of
great magnetic force.
But as is well understood the magnetic capacity of the needle depends upon the
mass of steel the needle contains provided of course that good steel be used and
therefore both the advantages mentioned above were not to be found united in the
same compass as an improvement in one direction generally resulted in a deterioration
in the other direction and there was consequently no advantage gained.
It is only by the aid of my improvements that it has become possible to construct
a compass in which lightness is combined with great magnetic force in such a degree
that the maximum of the magnetic momentum is reached.
-
This improved compass forms the subject of my present invention, which is
distinguished from compasses of old construction by perfectly answering the above
mentioned requirements as well as other requirements too, as my improved compass
has for instance not only exactly the same momentum of inertia upon all its axes
but also an accurate distribution of its poles so as to render the compass independent
of iron and steel being in its vicinity so far that neither sextant nor actant nor
decant deviations can arise.
By the aid of the great magnetic force of my improved compass the deleterious
influence of friction of the card and the needle as well as the resistance of the air
within the case are substantially compensated whilst on the other hand the compass
is constructed in such a way that the electric induction currents arising within the
metal of the case are employed in a highly advantageous manner for damping the
oscillations of the needle.
The magnetic disturbances can be compensated also in this system by magnetic.
means only but they may be distinguished from mechanical disturbances far better
than has been possible hitherto; thus a compensation may be effected with very
great accuracy and quadrant deviations for instance require a comparatively slight
quantity of soft iron for their compensation.
And in order that the said invention may be more clearly understood and readily
carried into effect I will proceed aided by the accompanying drawings more fully to
describe the same.

page_text: For the sake of clearness the magnets are drawn in all of the views somewhat
broader and thicker than they are actually employed in practice.
In carrying my invention into effect I take two magnets a b of semi circular shape
and connect them at their ends by parts e h of any non-magnetic material (the
specific gravity of which is approximately that of steel) in such a manner that a
ring is formed and that poles of the same names are at the same side.
The non-magnetic material used for the parts e and h serves for connecting the
magnets as well as well as for separating the poles of the same names.
I now form another ring of somewhat smaller diameter and constructed of
magnets cd connected by non-magnetic material fg and I connect both the rings
in the following manner.
A piece of silk k or any other suitable textile material provided with a rhumb
rose or compass card is placed over the smaller ring c d in such a manner that the
card is at the upperside and that the centre of the card coincides exactly with
the central point of the magnetic ring; the larger ring a b is now placed over the
smaller one c d so as to distend the silk and hold it down and the double ring which
forms the rim together with its cover now has the appearance shown in Figure 4
in which the inner ring ed gf and the space enclosed by it are covered by the
piece of silk k.
The central portion of the silk k is then provided with a conical shell or "dab" I
having in its apex a sapphire centre by means of which the whole arrangement inay
easily turn on the pin m which is secured in the bottom of the casing (not shown)
in any suitable manner.
Arranging the magnetic rings a bed in the manner shown in Figure 1 is of
practical value in all those cases in which nearness of magnetic disturbing iron is
avoided.
In cases where the magnetic disturbances arise from iron in the vicinity the
modification shown in Figure 2 may be employed.
In this arrangement both the rings a bed forming the rim are constructed in
exactly the same manner as in Figure 1 but the position of the rings in regard to
each other is altered in such a way that the magnetic poles are placed at an angle
of sixty degrees.
The effect of this arrangement excels considerably that shown in Figure 1 as a
compass of this construction is far less influenced by magnetic disturbances from
iron in the near vicinity.
Again in other cases the disturbances may be of so high a degree that the results
given with respect to the arrangements above described may not be of the desired
exactness.
For this reason the second modification shown in Figure 3 has been constructed
in which the inner magnets c d are of considerably less length than the outer
magnets.
The poles of the inner rings are at a distance of ninety six degrees, whilst those
of the outer rings are at a distance of twenty four degrees.
The advantages gained by this arrangement are perfectly exact for sextantal
actantal and decantal effects.
The manner of connecting both the rings is the same in all the arrangements
hereinbefore described and I wish it to be understood that for special purposes even
three or more magnets may be used, the positions of which with regard to each
other may be varied according to requirement.
The advantages gained by my improved construction are in general the
following:
Firstly. The magnetic momentum is extremely great compared with the slight
weight of the magnetic system.
Secondly. The weight is placed mainly at the periphery of the rhumb rose and
consequently the momentum of inertia is as great as possible.
Thirdly. The momenta of inertia of all the axes within the rim are of the
same value,

page_text: Fourthly. The magnetic axis of the magnet system may be determined and
controlled easily by turning one of the rings constituting the rim in relation to
the other.
Fifthly. The card may be made transparent in lieu of opaque to facilitate
illumination from below.
Sixthly. The construction may be of great strength requiring practically no
repairs and yet of moderate price.
I wish it further to be understood that every alteration in the number of magnets
and the number of rings in the diameter and the form of the rings or in their
breadth in the arrangement of the magnets or rings with regard to each other, in
the manner of fixing the silk card, comes within the scope of my invention, which
consist in its main points in replacing the straight magnets or needles used hitherto
by annular magnets composed of two or more parts and by the arrangement of one
or more of such rings for the purpose stated.
I am well aware that there exists already a compass card of somewhat similar
appearance, invented by one Duchemin, this card differs however very much from
my construction as I compose the rings of two or more magnets whilst Duchemin
employs an uninterrupted ring of steel magnetized so as to act like a simple straight
magnet.
In this latter construction a displacement of the magnetic axis may easily occur
such an incident being quite impossible in my compass.
Moreover Duchemin's compass does not answer in the least the requirements
stated in the preface hereto, as its construction requires a great deal of non-
magnetic material, whilst I employ but very little, and that merely for separating
poles of the same names as above described.
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 a magnetic compass the combination of two or more curved magnets, with
parts of any non magnetic material said parts connecting the magnets, so as to form
rings and separating poles of the same names; substantially as and for the purpose
described.
2. In a magnetic compass the combination of a magnet ring system composed of
two or more curved magnets (a 6 or cd) and of parts of non-magnetic materials (e h
or fg) inserted between poles of the same names with one or more magnet ring
systems of similar construction one ring being placed within the other substantially
as and for the purpose described.
3. In a magnetic compass the combination of one or more magnet systems each
composed of two or more magnets (a b or cd) with a card k made of silk or the
like, said card covering the space enclosed by the rings, the whole device being
adapted to rotate on a needle or axis substantially as and for the purpose described.
Dated this 18th day of July 1891.
WHITE & WOODINGTON,
27, Southampton Buildings, London, Agents.