Improvements in Mariners' Compasses.
Year: 1895

page_text: Date of Application, 10th Dec., 1895-Accepted, 4th Apr., 1896
Improvements in Mariners' Compasses.
A communication to me from THE SIRIEIX MARINERS' COMPASS COMPANY,' of
533, Kearney Street, in the City and County of San Francisco, California,
United States of America.
I, EDMUND EDWARDS, of the Firm of Edwards and Co., Patent Agents and
Engineers, of 65 and 66, Chancery Lane, in the County of Middlesex, 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, and accompanying drawings, (that is to say):-
--
This invention relates to mariners compasses and my object is to provide a simple
and effective device for correcting the deviations of the magnetic needle arising
from the disturbing influences of magnetic bodies in proximity to the compass.
The influence of such magnetic bodies when forming a part of the structure of
the vessel is termed sub-permanent magnetism. The influence of magnetic bodies
not charged with magnetism is due to magnetic induction. Sub-permanent
magnetism is inherent in iron and steel built vessels. Induction magnetism is also
present in such vessels, as well as in wooden vessels provided with machinery,
smoke-stacks, guns, etc., or loaded with iron or steel cargo.
It is well known that an iron or steel ship while being built, or when for a length
of time occupying a certain position relatively to the terrestrial magnetic poles,
induces some magnetism, and thus becomes a magnet. This magnetism is called
sub-permanent magnetism, and is subject to alteration by natural or accidental
causes, such as by travel for a long time in the same direction, by concussion, etc.
Preliminary to a description of my invention I will state briefly what the
deviations of the compass are, from the different influences which can affect it.
-
The deviation produced by the sub-permanent magnetism of the structure is
called a semi-circular deviation; and it depends upon the magnetic polarity of
the ship. This in turn depends upon the position of the ship in the building dock
relatively to the terrestrial magnetic poles. The symbols to express the deviation
may be termed co-efficients: + B and B according as the compass deviates
toward stern or bow, as the result of the sub-permanent magnetism induced by a
position north or south in building and +C and C as the result of sub-
permanent magnetism induced in the vessel when built with her bow toward the
west or toward the east. In any case there is always a co-efficient + C and - C
in the ship, even if she has not been built in the latter position.
-
Iron or steel, which may be parts of the ship, such as machinery, guns or
funnels, or separate bodies, such as cargo, acts upon the compass in two ways:
vertically and horizontally. The deviation is quadrantal produced by iron
horizontal with the compass and is expressed by the symbols + D and D. The
deviation consequent upon iron placed vertically, relatively to the compass, is a
compound deviation with the semi-circular B and C.
-
-
―
- A
There is also an octantal deviation produced by iron at 45°, which I express
by + E and
E. The remaining errors are the heeling errors + K and K
produced by the listing of the ship to port or starboard, and an error + A or
produced by the unsymmetrical disposition of iron. This latter is a constant.
quantity no matter what the direction of the ship is, and when sufficient care is
taken need not be considered.
My invention provides a device by which all these co-efficients of error can be

page_text: corrected and the principal feature of my invention consists in the employment of
ring magnets as compensators instead of bar magnets, as commonly used. In
addition to this, my invention comprises various special features of construction
which are fully hereinafter described and which make a simple, efficient, and
thoroughly practical compensated compass.
My invention is fully illustrated in the accompanying drawings, in connection
with which the Specification should be read.
Fig. 1, is a central vertical section of the entire compass;
Fig. 2, top plan of compass card broken away to show the ring magnet attached
to its lower surface;
Fig. 3, is a plan view showing the adjustable induction block;
Fig. 4, is a cross-section through the lower compartment of the compass case,
with the adjustable compensating disk removed;
Fig. 5, is a bottom plan of the adjustable compensating disk;
Fig. 6, is a cross-section on line - of Fig. 3, showing induction blocks;
Fig. 7, is a development of the separate sections of one of the ring magnets to
clearly show their relations to each other.
The compass case A is a shell or cylinder provided with knife edged trunnions 1,
by which it is hung in the binnacle. The case is preferably divided by a
horizontal partition 2 into upper and lower compartments. On the partition 2,
and in the upper compartment is mounted the standard 3, which supports the
pivot 4, upon which the compass card B turns in a hardened bearing 5 of agate or
other suitable substance. I prefer to secure to the card a sleeve and cap 6, having
a projecting needle 7 which is in close proximity to the glass protecting plate 8.
This plate is held in place by a snap-ring 9. To the bottom of the compass card
and surrounding its pivot is a ring magnet C of peculiar construction. Several of
these rings are used in different situations in the compass, and in describing the
construction of the ring C, I shall be describing that of the others as well, so that
the latter will be understood when referred to hereinafter. The ring is shown as
composed of two sections of band steel tempered like a clock spring and formed
into a spiral coil. (See Fig. 7.)
One section is slightly longer than the other and their measurement is such that
when coiled each section will make one and one-half turns of the complete ring, its
ends reaching exactly both ends of a given diameter of the ring. One section,
(the shorter) being laid as described, the second is continued from the outer end of
the first, tightly overlapping the latter and, after one and one-half turns, reaching
the radial line at which the first section started. Thus the shorter or inner section
begins with its north pole N. and after one and one-half turns terminates at its
south pole S. opposite. The outer section begins with its south pole, and after one
and one-half turns, ends at N. its north pole. Thus a two-section ring has three
complete turus or circuits, while a ring cau be made of four sections in the same
way, giving six of such circuits, or of a greater number of sections in the same
proportion. The points X and Y at 90° from the poles are perfectly neutral.
When the ring is properly charged it exhibits at each extremity of a certain
diameter, a precise point where the magnetism is at a maximum intensity; while
the diameter at right angles with the former shows at each extremity another
precise point where the magnetism is absolutely neutral. It therefore has, like a
bar magnet, two opposite poles, but has two opposite neutral points, making it a
true magnet. It possesses for this purpose great advantages over a bar magnet,
having a higher degree of power and greater sensibility, precision and stability.
It renders the card steadier and prevents the excessive vibrations to which bar
magnets expose the card. This ring, as stated before, is attached to the compass
card with its poles in proper position relatively to the points marked on the card.
Within this ring are four magnetic bars D Figure 2 set edgewise and distaut 30°
from one another, and in such position that their poles touch the ring, and their
polarities correspond with those in the magnetic fields of the ring. The ring and
bars act collectively as the needle of the compass.

page_text: Mounted in the upper compartment of the compass case are the induction
blocks E E for the compensation of quadrantal deviation. Each block is a piece of
soft iron secured to a slide E¹. The slides are adjusted toward or away from one
another, upon a guide-strip or frame F placed upon the partition and having the
standard which supports the compass card passing through it. A rod 10 having
right and left hand threads is fitted to bearings in the guide F and also to
correspondingly threaded projections 11, on the slide E'. The compass case is
slotted (Figs. 1 and 3) and through the slot can be inserted handles 12 and 13, one
of which 12 is used to turn the screw rod 10, and move the induction blocks
simultaneously, either inwardly or outwardly, and the other 13 for turning the
guide F and induction blocks horizontally. The proper position of these induction
blocks can always be determined by the operator moving them in or out, or
adjusting them horizontally until the compass indicates true magnetic north.
The compensating devices for sub-permanent magnetism or semi-circular
deviation is composed of two parts. First, a known and constant quantity
consisting of a ring magnet G fixed to a disk G¹ upon a movable strip Hat the
bottom of the compass. bowl or case. This ring G is like the one before fully
explained. The poles of this magnet are in line with the axis of the ship or
parallel to it. This known quantity is inserted in order that the compass may be
used in wooden ships, where little or no sub-permanent magnetism exists but where
the principal deviations are due to incoming cargo of iron, etc. In other words
this constant quantity can be used to neutralize the compensation for sub-permanent
magnetism under conditions where the latter does not exist.
The second part is the compensation for sub-permanent magnetism or semi-
circular deviation which has yet to be described. This is a vertically adjustable
compensator in the lower compartment, consisting of a ring magnet L, similar to
those before described, but the polarity of which is directed in a field opposite to
the magnetism of the ship, and opposite to that of the known quantity just
referred to.
A brass disk M carries the ring magnet L within which are secured sixteen
small ring magnets N, each constructed like the large magnet which surrounds
them. These magnets N are arranged in two series of eight each, the series being
separated by a soft iron washer. 14, with which all the magnets N are in contact
(Fig. 1); and such magnets are also, each and all in contact with the surrounding
magnet L, their poles being in the same magnetic field. The magnets of a series
overlap two similar magnets of the other series, as clearly indicated in Fig. 5.
The correcting power of this magnetic ring is proportionate to the quantity
required for all necessary compensation of semi-circular deviation, and is of course
regulated by its vertical altitude relatively to the compass card. This disk and
magnets are mounted by nuts 15, 16 upon a screw O rising from the bottom of the
compass, case, and which can be turned by a projecting handle 17 and held by
a check nut 18. Guides 19 rising from the strip H and passing through the
disk M ensure the vertical movement of the latter but prevent it from turning.
The ring compensator is adjusted to the line of the ships magnetism by moving
the lower bar or strip H horizontally, thereby moving also the disk M and its ring
magnet, the two magnets L and G being always in the same position relatively to
each other, so far as horizontal motion is concerned; but, as their polarities are
opposed, it will readily be seen that by adjusting the magnet L downwardly until
it meets and enters within the magnet G, it will be neutralized by the latter and
will exert no effect upon the compass card. This fully explains the statement
before made that in wooden ships the lower magnet was used to neutralize the
upper. In steel and iron vessels where the deviations occur which are corrected
by the magnet L and its rings, such magnet must be adjusted upwardly from the
magnet G (Fig. 1) before it becomes effective.
The horizontal adjustment of the constant magnet and the adjustable
compensating ring is simply and easily performed by means of the pin 20 which

page_text: projects through the compass case, and is secured to the strip H a slot 21 (dotted
lires Fig. 4) being provided in the case to permit it to be moved.
The compensation for semi-circular deviation and for quadrantal deviation, are
thoroughly made by the devices herein described. The remaining deviations when
present are compensated by well known devices forming no part of my invention
and not shown in the drawing, but referred to here for the sake of completeness.
These are deviations due to vertical iron, such as the masts of the ship, the rudder
post, etc., for which the Flinders bar is used in a well known way. The other is
the heeling error, which is compensated by a bar magnet placed below the
compass in an equally well known way.
The theory of compensation for this compass rests on general and well known
laws.
Like other compensated compasses it presents compensation for all
disturbing influences, but unlike them, it combines all the elements of compensa-
tion in small space. It affords by adjustment a magnetic force equal in intensity
and contrary in direction to the resulting forces of all magnetic actions, attractions
and repulsions derived from the proximity of all magnetic bodies, without in any
way interfering with the action of terrestrial magnetism.
In adjusting the compass, supposing the ship to be at the port of regulation, or
under steam or sail in sight of bearings, the adjuster will first see that the soft iron
induction blocks, in the upper compartment, are set at right angles to the lubber
line. He also raises the compensating disk in the lower compartment about half
way up the adjusting screw, or some distance from the constant magnetic ring.
Having taken his bearings, he now turns his ship to correct north or south
magnetic. If the card should not show north he will adjust the lower compensa-
tion horizontally right or left, as the case may be, so as to bring the compensation
into position with its magnetic field in line with the magnetic forces of the ship
and thus bring the card to show north. He will now turn the ship to correct east
or west magnetic, and will determine by observation whether and how much it is
necessary to adjust the ring compensation vertically to bring the needle to correct
north. The compass is now adjusted for sub-permanent magnetism. The deviation
from horizontal iron will be corrected with the ship turned into quadrantal position,
by adjusting the induction blocks in the upper compartment toward or from the
pivot of the compass, until the card again indicates correct north.
The use of this compass permits of an immediate adjustment with two bearings
at 90°,
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In a compass, and in combination with the compass card, an all magnetic ring
without projections attached to such ring, substantially as described.
2. In a compass, and in combination with the compass card, an all magnetic ring
without projections attached to the ring, parallel bar magnets connecting the
opposing magnetic fields in such ring, substantially as described.
3. A magnetic ring for a compass formed of separate spiral sections, each
section terminating in a magnetic pole in proximity to a magnetic pole of like
polarity on another section, substantially as described.
4. A magnetic ring for a compass, formed of two spiral sections coiled one
within the other and having two poles each, arranged in proximity to corre-
sponding poles on the other section, and all terminating at a line which is a
diameter of the complete ring, substantially as described.
5. In a compass, a compensator for sub-permanent magnetism, consisting of a
magnetic ring having opposite poles at the ends of one of its diameters, and ring
magnets enclosed by and in contact with such ring substantially as described.
6. In a compass, a compensator for sub-permanent magnetism, consisting of a
magnetic ring having opposite poles at the ends of one of its diameters, two series

page_text: of ring magnets enclosed by and in contact with such ring, and a washer or plate.
of soft iron in contact with both series of enclosed ring magnets, substantially as
described.
7. In a compass, and in combination with the compass card, a compensator for
sub-permanent magnetism consisting of a magnetic ring having opposing poles at
the ends of one of its diameters and ring magnets enclosed by and in contact with
such ring, and means for adjusting such ring vertically relatively to the compass.
card, substantially as described.
8. In a compass, the combination with the compass card of a compensating ring.
of a determined polarity which opposes the determined sub-permanent magnetism.
of a ship, a neutralizing ring of opposite polarity to said compensating ring, and
means for adjusting said compensating ring toward and from the compass card and.
toward and from the neutralizing ring, substantially as described.
9. In a compass and in combination, a compass card, a compensating magnetic
ring vertically adjustable, a neutralizing ring of constant and opposing magnetic
polarity, a connection between said rings which permits the vertical adjustment of
the former, and means for moving the constant ring horizontally and thereby
adjusting the compensating ring simultaneously and horizontally, substantially as
described.
10. In a compass and in combination with the compass card and slotted compass.
case, a guide pivoted in the compass case, induction blocks supported upon said.
guide and a right and left threaded rod engaging with the supports for said.
induction blocks, substantially as described.
Dated this 10th don nt
L1005
EDWARDS & Co.,
65 and 66 Chancery Lane, London, Agents for the Applicant.