Improvements in Ships' Compasses.
Year: 1889

page_text: Improvements in Ships' Compasses.
We, THEODOR CORNELIUS KNUDSEN, Optical instrument maker and ANTON
NÖRHOLM, Engineer, both of 37 Store Kjóbmagergade Copenhagen, Denmark, 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:-
Permanent magnets of varying size and strength have heretofore, as is well known,
been applied near the compass in order to annul or counteract the so-called local
attraction or the influence of the iron masses of the ship thereon. The mode in
which this has hitherto been done had, however, many and important defects, chiefly
that the regulation of the compasses (which, owing to the alterations in the local
attraction and the magnetic circumstances present was frequently required in long
and even in short journeys) was difficult and tedious. But the first adjustment of
the compasses has hitherto also been difficult and the magnets arranged on the
ship are often in the way.
By one of the improvements now to be described we collect all the magnets for
annulling or compensating for the so-called semi-circular or cardinal error and the
heeling error upon a small standard or framing which is arranged under the middle
of the compass and wherein the magnets which then need only be comparatively
small can be adjusted and as required, changed so that the two said deviations may be
easily counteracted.
Figure 1 is a side view and Figure 2 a plan of this apparatus. The standard of
the apparatus consists of a vertical tube A open at both ends or at the top only and
having a foot B whereby it is fixed by screws in the compass pedestal or stand
below the middle of the compass. The tube has two longitudinal slots (one of
which C, is only shewn in Figure 1) and wherein two blocks or slides D, and D₂ can
slide up and down and be fixed at any height by set screws E, and E, passing
therethrough and into bearing or gripping pieces F₁ and F, within the tube. Each
block forms a bearing 1, and I, for one or more magnets G, and G, (two are shown
here) which are placed exactly centrally of their length in the blocks and are fixed
by set screws H₁ and H₂. These magnets serve only for counteracting the semi-
circular or cardinal error. The blocks D1 D2 are so placed that the magnets G₁
and G, form an angle of 90° with each other, and as the blocks are moved up
and down in the pipe A the magnets always keep parallel with the same straight
line.
Besides these two longitudinal slots there is in the pipe A a third longitudinal

page_text: :
slot serving for guiding a third block or slide D³ which however is inside the tube A
and is pressed against the inner side of same. It can be fixed at any desired height
by means of the set screw E, which passes through an outer bearing piece F, and
screws into the block D. The block D³ serves to hold a vertical magnet G3 in
the axis of the tube which magnet serves to compensate for the heeling error.
The
block D, has a suitable bearing or eye l₂ and a set screw H, for fixing the magnet G
therein.
The invention next consists in means for counteracting the quadrantal error, viz.,
a circular row of cylinders of very soft iron which are adjustable vertically
and are placed radially to the compass. As long as these cylinders lie in a
common horizontal plane and level with the compass needles, they will by their united
influence strengthen the adjusting power of the compass needles. If larger or smaller
parts of the row are lowered more or less below the height in which they are nearest
to the needles the influence of those parts upon the needles will be reduced the more
they are lowered, hence the cylinders which are not lowered so much and which are
nearest to the magnet needles will overpower the cylinders which are still more
lowered and will together with them when placed in a certain direction, produce a
quadrantal error which can be utilized for annulling the quadrantal error produced
by the local attraction in the ship.
This improvement is illustrated by Figures 3 and 4, Figure 3 being a side elevation
of the compass with a row of cylinders and Figure 4 is a half plan of the row of iron
cylinders and parts belonging thereto, but without the compass itself.
A is the compass itself, B, B, B3 the iron cylinders or rods and C a horizontal
ring which can be adjusted vertically and wherein the cylinders are placed. D D are
arms which connect the ring C with the boss E; the latter encloses loosely a screwed
pivot F on the bottom of the compass. Jis a nut on the pivot F, this nut is in a slot in
the boss E, so that by turning the nut the ring C can be raised or lowered relatively
to the compass. The two cylinders B, diametrically opposite to each other are not
to partake in the aforesaid up and down motion, wherefore they have their bearings
in upright rim pieces G on two arms H which are adjustably fixed to the underside
of the compass by means of set screws which pass up through slots in the plate
forming the arms H and are concentric with the compass. The cylinders B³ will
only rest in their bearings in the ring C when the latter has been screwed up to its
uppermost position wherein it is stopped by the cylinders B. The bearings in the
rim pieces G will in all positions of the ring C reach up between those cylinders
which have their bearings in the ring C so that the latter thereby is always compelled
to follow the arms H when these are turned around the screw F on the compass for
adjusting the cylinders B, in the horizontal circle all according as the iron masses in
the ship require it. The cylinders B2 have also suitable lower bearings arranged
stepwise in the rim pieces G and the bearings for these cylinders are notched out
from below in the full ring so that they can leave these notches or bearings when
they in the lowering of the ring C by means of the nut J and screw F enter their
bearings in the rim pieces G.
In order that the ring thereupon with the other cylinders therein can be further
lowered for obtaining a firm and sure rest for the cylinders B, either in their
bearings in the ring or in the rim pieces G they are enclosed by rings or eyes K
'on the rods L which are screwed in from below and reach down through holes in the
ring C and in the arms H. Below the latter the rods L are provided with helical
springs M between the bottom of the arms H and the heads on the rods L. The
springs M press the cylinders B2 with sufficient force down into their bearings.
When the ring C is raised to its uppermost position as shown in Figure 3 all the
cylinders B B and B³ are in a horizontal circle round the compass bowl level with
the magnet needles on the card.
The cylinders B, B, B, will therefore produce no deviation of the compass card but
they serve as stated, to give the compass card power to adjust itself..
If the ring C is lowered two curved surfaces will be formed which are diametrically
opposite to each other and whose curvature will be so much greater the further the

page_text: ring C is lowered but only up to a certain limit in that the bearings for the
cylinders B in the rim pieces G are cut so much deeper the further they are
removed from the cylinders B, in the rim piece in question. During the lowering of
the ring C the cylinders B₂ remain horizontal and radial to the compass. The two
curved surfaces which the rods B, and B, will form by the lowering of the ring C
produce together a deviation of the compass card on the courses NE, SE, SW
and NW which becomes so much larger, the larger the curvatures of the said
surfaces are, or the more the ring C is lowered and this deviation can be utilized
for annulling the quadrantal error from the local attractions if first by the aforesaid
half circular_error be annulled while the ship is laid to the course NE to SW
or NW to SE or vice versa. Besides raising or lowering the ring C for counteracting
the quadrantal error it may also together with the rin pieces G and all the
rods B, B, and B, be adjusted by turning the same round the compass.
'
If the quadrantal error in the ship is positive then the rods are so adjusted that B3
is athwartship but if the quadrantal error is negative, then the aforesaid set screws for
holding the arms H are loosened and the arms H and ring C turned so far that the
rods B stand fore and aft and the set screws again screwed into corresponding holes
at the underside of the compass. When there are unsymmetrical masses of iron in
the ship in the vicinity of the compass, a deviation arises which is sometimes called the
constant E." The slots I in the arms H serve to annul this error as the arms Hand
the ring C can be turned to the right or the left according as the "constant E"
appears as positive or negative.
In compasses having a card of less than 6 inches in diameter the construction in
Figures 5 to 8 may be used for annulling the quadrantal error Figure 5 being a side
view of a compass with its row of surrounding iron rods in their highest position, the
dotted lines showing them in the lowest position. Figure 6 is a half plan of the row of
rods B₁ B₂ B, the compass itself being omitted Figures 7 and 8 are details.
This construction differs from the one shown in Figures 3 and 4 merely therein
that the bearings of the fixed rods B are fixed to the bowl itself in that the ring C is
not entire but interrupted for a shorter or longer distance below the fixed rods B and
finally in that the rods B, are carried in the joint pieces H, and H, which at one end
are fixed to the bearings of the fixed rods B, while their other end is connected to the
end of the ring C by means of a pin I and a slot Q. In the lowering of the ring C
from the position shown in full lines in Figure 5 the pieces H, H, will be more or less
inclined according to the amount of lowering thus producing the larger or smaller
curvatures in the ring of the rods.
This construction is not so suitable for larger compasses because the rods B, in the
lowering of the ring C, come in a more or less inclined position which may be
disturbing when the rods around the compass are of considerable length.
A further improvement relates to the construction of the compass card and especially
the mode of fixing the magnet needles thereto, Fig. 9 is a plan and Fig. 10 a side
view of such a compass card.
The card is fixed on a ring s made of very thin angle shaped sheet metal.
The ring is united to a cap in the centre by means of small thin walled pipes.v
and 2. On each of the pipes v, is fixed a small T shaped piece of sheet metal w
the head of which forms a rod under the card and the flange of which is provided
with holes for inserting the compass needles y. In order to avoid soldering which
would impair the magnetic properties of the needles y, the latter have grooves
turned in them as shown at z, Fig. 12, so that the needles need only be pressed
through the holes in the rods w in order to be sufficiently firmly fixed. The
T pieces w are pressed concave as shown in longitudinal section in Fig. 11 in
order to afford lightness and strength.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed we declare that what we
claim is
First-The improved construction of ships' compasses in which the binnacle

page_text: casing is provided with a surrounding horizontal row of radial cylinders or rods B₁ B₂
and B3 Figs. 3 to S of which some B₁ and B₂ can be lowered more or less by
turning the nut J on the screw F which descends from the compass bowl, while
other cylinders B₁ remain in their position so that the row is changed, from a flat
row into a more or less undulating one for the purpose of annulling or obviating
the deviations from local attractions.
Second In ships' compasses, the application of the fixed rim pieces G Figs. 3
and 4 having stepwise arranged bearings for some of the cylinders viz. for the
cylinders B, which by the lowering of the ring C wherein all the cylinders B, and B'
have their bearings in the uppermost position, leave their bearings in the ring and
during the further lowering of the ring, remain in their bearings in the rim
pieces G for the purpose of producing the undulating formation of the row of
cylinders.
Third In ships' compasses the application to the compass bowl of the descending
screwed spindle F in combination with the nut J which works in a slot of the
boss E, Figs. 3 and 5 for the purpose of raising and lowering the ring C.
Fourth In ships' compasses, the permanent placing of the cylinders B3 in the
rim pieces G and their fixing to the arms H, Fig. 4 which can he turned round
the screwed rod F that descends from the compass bowl and can be fixed in various
positions relatively to the local attractions in the ship whereby the whole row of
cylinders B₁ B, and B, can be adjusted as required.
Fifth-In ships' compasses, the application of the joint pieces H₁ and H,
Figs. 5 to 8 forming bearings for the cylinders B, and which at one end are jointed
to the compass bowl or to a part fixed thereon and at their other end are connected
with the ring by means of pin I in the slot Q.
Sixth-In ships' compasses, the application of a standard Figs. 1 and 2 arranged
below the compass and consisting of the pipe A having slots C₁ with blocks or
slides D D and D, which can be set by means of screws and have bearings I₁₁₂
and 1, for the magnets G₁ G, and G, all for the purpose of annulling the so called
half circular and heeling errors by adjustment of the magnets G₁ G² and G³.
Seventh-The application of a compass card in which the card proper r,
Figs. 9 to 12, is fixed to a rings of angular sheet metal said ring being connected
to the cap t in the middle by pipes, and having thin walls.
Eighth-In compass cards fixing the needles to the card by means of thin
concave pressed T shaped pieces of sheet metal w, the stems of which are fixed
to the card and the heads of which have holes into which the magnet needles y are
pressed until the pieces whold the needles in grooves z formed therein.
Ninth The improved constructions of compass correctors for the semicircular
error and heeling error and quadrantal error substantially as shown in the drawings.
Tenth -The improved construction of compass card substantially as shown in the
drawings.
Dated this yth day of March 1889.
THEODOR CORNELIUS KNUDSEN.
ANTON NÖRHOLM.
By Jensen & Son,
7.7, Chancery Lane, London, W.C.,
Patent Agents.