IMPROVEMENTS IN COMPASSES FOR SHIP AND OTHER USE
Year: 1884

page_text: COMPLETE SPECIFICATION.
"
I THOMAS WATSON BRUCE, of 27, Wapping, in the City of Liverpool and
County of Lancaster, Optician and Compass maker do hereby declare the nature
of my invention for "IMPROVEMENTS IN COMPASSES FOR SHIP AND OTHER USE
and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement :—
This invention has for its object a compass which will be able to withstand
more perfectly the shocks incidental to sea use. In the ordinary compass the card
is of considerable weight and the bearings and pivots have to be designed so as to.
withstand the momentum of this weight under such shocks. To lessen the effect
of shocks the bowl containing the card is usually in steam Ships hung in the
gimbals by india rubber spring fastenings. India rubber is however very liable
especially in hot climates to decay or become altered into á hard brittle material.
Now my invention is designed to avoid these evils. It is best described by aid
of the accompanying drawings, in which Fig. 1 is a plan of card, Fig. 2 is a plan of
the attachment of the bowl to the gimbals when a strain has been brought to bear
upon it sufficient to bring the safety chain into play, and Fig. 3 front elevation of
same. Fig. 4 plan of card.
Referring first to Fig. 1, A. is a light metallic ring shown in dotted lines. BB BB
four brass or other non-magnetic metal wires crossing at right angles, and
preferably at equal distances from the centre of the card and firmly secured at
their ends to the ring A by soldering or otherwise. These with the ring form an
admirably strong light frame and are a very valuable part of my invention. CC a
series of light magnets formed of watch spring steel and fastened to the wires B B
by waxed threads at each end. They could be fastened in other ways, but I have
found these waxed threads very superior as a fastening to the arrangements at
present adopted. D central bearing for pivot fastened to sheet F. sheet of
tracing cloth, glazed silk, or other light strong material carrying the bearing D
firmly secured to it in any convenient manner. The sheet F is pasted over the
wires B so as to be firmly stretched and securely held to the wires, forming a very
light and springy framework to attach the pivot bearing to. NSE and W at the
four cardinal points are pieces of tracing cloth; glazed silk, or other light strong.
material little altered in dimensions by heat, uniting the sheet F with G G. GG
annular dial or card of compass formed in four pieces pasted over the annular
frame, and either in one with the pieces NSE and W or separate, and united to
them by sewing on both sides instead of at one only as shown at H H in the

page_text: ·
drawing, where they are each depicted in one piece with one of the NE S or W
pieces in each case.
.
It will be seen that the entire card is composed of a very light skeleton frame, a
thin membraneous matter forming the compass points and scale, the bearing and
some very light magnets. A card of this description 18 inches in diameter only
weighs a few ounces instead of as with ordinary cards of similar size weighing
three quarters of a pound or more.
The scale being formed in several pieces allows for expansion and contraction, so
does not curl up. As a card of this light delicate nature would be apt to be
damaged by sudden shocks, I suspend the bowl more carefully than with ordinary
cards. Referring to Figs. 2, 3 and 4 which show my suspension arrangement, J is
the bowl, K the gimbals, L and M two plates, brazed or otherwise attached to the
gimbal and bowl respectively and holding the springs and chain hereafter described
more securely. N N are two bent wire springs attached at each end to the bowl
and gimbals respectively by the plates L and M which are screwed in position as
shown. Pa safety chain fitting in a slot between the plates Land M and the
gimbal and bowl respectively, and screwed up tight. This prevents too great a
strain being brought by careless hands or otherwise on the springs. There are
four or more spring attachments on each compass on opposite sides each formed of
springs as shown. Other forms of springs could however be used with almost
equally good results.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is
1st. The light but strong cards for compasses formed of light materials and
arranged and constructed substantially as described.
2nd. The manufacture of compasses with the bowl suspended from the gimbals
by means of metallic springs substantially as described, also in combination with
these the safety chain P for the purposes described.
Dated his gord 1
T1
1004