IMPROVEMENTS IN APPARATUS FOR SHOWING THE SPEED OF SHIPS
Year: 1882

page_text: LETTERS PATENT to Thomas Davison, of Glasgow, in the County of Lanark,
North Britain, Engineer for an Invention of IMPROVEMENTS IN APPARATUS
FOR SHOWING THE SPEED OF SHIPS.
PROVISIONAL SPECIFICATION left by the said Thomas Davison at the Office
of the Commissioners of Patents on the 23rd February 1882.
THOMAS DAVISON, of Glasgow, in the County of Lanark, North Britain,
Engineer, "IMPROVEMENTS IN APPARATUS FOR SHOWING THE SPEED OF SHIPS."
”
This Invention relates to apparatus arranged to obtain indications of the speed
of a ship from the pressure of the water on an instrument carried by the ship; and
an important feature of the Invention consists in placing the instrument on which
the pressure is to act in a position where the water is disturbed to the least
possible extent. The Invention also comprises improvements in the details of the
apparatus.
In one modification of the apparatus a small plunger to be acted on by the water
pressure on its outer and is fitted so that it can slide in the front end of a tube
which is horizontal or nearly so when in use. A spring is applied to the plunger
to resist the pressure so that the movement inwards of the plunger may correspond
to the greater or less pressure, or in other words the greater or less speed of the
ship. The water has access into the tube behind the plunger by one or more
openings in the side of the tube for the purpose of balancing any pressure on the
front of the plunger due to mere depth in the water. A rod extends back from
the plunger and has a toothed rack at or near its back end which gears with a
pinion on the lower end of a spindle extending upwards through a tube to an
indicating dial above. At or near the junction between the horizontal and vertical
tubes, arms or stays are fitted to the apparatus to bear against the ship and keep
the horizontal tube in a proper position. The horizontal tube is to be applied at the
bow of the ship and it is to be of such a length that its front end may be in water
which is at rest and unbroken or nearly so. The necessary length of tube will vary
with different ships, a comparatively small length-say one to three feet for sharp

page_text: or fine-lined ships such as steamers and greater lengths for ships having bluffer
bows. Instead of a plain plunger, the part to receive the pressure of the water
may be a ball on the front end of a rod projecting from the horizontal tube.
In a second modification of the apparatus a small rubber bag containing air is
placed within the front end of the horizontal tube and is separated by a diaphragm
or disc from a second rubber bag containing air, the water having access to the
outside of the second bag through openings in the side of the tube. From the two
bags small tubes proceed to indicating apparatus placed in any convenient situation.
One form of indicating apparatus is a mercurial siphon or U-tube supported in
gimbals and baving the small tubes from the rubber bags connected so that the
pressures in the tubes may act in opposite directions on the mercury.
mercurial tube is of glass and the speed is shown by the difference of height between
the two columns of mercury.
The
In other modifications a small screw or a rotating set of hemispheres, may be
used for receiving the pressure of the water at the front end of the horizontal tube
the motion imparted thereto being transmitted through small spindles and
worm wheel gearing to indicating or counting mechanism on deck. With some
modifications of the apparatus combined with suitable clockwork the variations
of the speed or the distance passed through by the ship may be recorded.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Thomas Davison in the Great Seal Patent Office on the 19th August
1882.
THOMAS DAVISON, of Glasgow, in the County of Lanark, North Britain,
Engineer. "IMPROVEMENTS IN APPARATUS FOR SHOWING THE SPEED OF SHIPS."
My said Invention relates to apparatus arranged to obtain indications of the
speed of a ship from the pressure of the water on an instrument carried by the
ship; and an important feature of my Invention consists in placing the instrument
on which the pressure is to act in a position where the water is disturbed to the
least possible extent. My Invention also comprises improvements in the details of
the apparatus.
In one modification of my apparatus a small plunger to be acted on by the water
pressure is fitted to slide in the front end of a tube which is horizontal or nearly
so when in use. The horizontal tube is to be applied at the bow of the ship and it
is to be of such a length that its front end may be in water which is at rest and
unbroken or nearly so. The necessary length of tube will vary with different
ships, a comparatively small length say one to three feet for sharp fine-lined ships
such as steamers, and greater lengths for ships having bluffer bows. Instead of a
plain plunger the part to receive the pressure of the water may be a ball on the
front end of a rod projecting from the horizontal tube. Or a small screw or a
rotating set of hemispheres may be used for receiving the pressure of the water at
the front end of the horizontal tube.
In other modifications two small tubes are provided in connection with the two
ends of a mercurial siphon or U-tube and one of these small tubes is arranged to
transmit the pressure due to the depth of the water and to the movement through
the water and which acts at the front end of the main horizontal tube, whilst the
other small tube transmits the pressure due to the depth of water in which the
main horizontal tube moves in a manner to balance that part of the pressure in the
other small tube which is due to the depth, so that the resultant action on the
mercury may be that due to the forward motion only. Any other suitable
pressure indicating apparatus may be used instead of the mercurial siphon.
And in order that my said Invention and the manner of performing the same
may be properly understood I hereunto append three sheets of explanatory
drawings to be hereinafter referred to and representing various modifications of
my improved apparatus.
Figure, 1, of the accompanying drawings is a front elevation of the bow of a
ship with one modification of my speed indicating apparatus applied to it; and
figure, 2, is a corresponding sectional plan. Figures, 3, and 4, are similar views
showing a second modification; and figures, 5, and 6, are similar views showing a
third modification. Figures, 7, and 8, are a plan and side elevation of the
indicating apparatus shown in figures, 1 and 2, but drawn to a larger scale, and
figures, 9, and 10, are vertical sections as at right angles to each other, of the same
apparatus drawn to a still larger scale. Figures 11 and 12, are vertical sections as
at right angles to each other of a modification differing from that shown in
figures, 9, and 10, and figure, 13, is a vertical section drawn to an enlarged scale
corresponding to figures, 5 and 6. In these drawings the same reference numerals
are used to mark the same or like parts wherever they are repeated
In the modification shown in figures, 1, 2, 7, 8, 9, and 10, a small screw, 14, is
the instrument acted on by the pressure of the water due to the forward motion
of the ship.
It is made with blades the outer parts of which are curved or
extended backwards so as to throw off any floating weeds or other matters which

page_text: they may encounter. The screw, 14, is on the front end of a spindle, 15, which is
carried by and projects from the front end of the main horizontal tube, 16. The
back end of this main horizontal tube, 16, has fixed to it a saddle piece, 17, to bear
upon the stem, 18, of the ship; and the saddle piece, 17, has fixed to it arms, 19,
which extending backwards horizontally in divergent directions and having blades
fixed at their after ends, serve through the action of the water on them to keep
the apparatus steady with the main horizontal tube 16 directed properly forwards.
At a part a little in front of the saddle piece, 17, the main horizontal tube, 16, has
fixed to it a vertical tube, 20, which extending up to the top of the stem, 18, of the
ship serves to support the apparatus and for other purposes, and is held in a guide
or clamp, 21, at the top of the stem. An arm or lever, 22, extending backward is
fixed to the top or upper part of the vertical tube, 20, and serves for bandling and
steading the apparatus; and the tube, 20, is surmounted by a box, 23, containing
a dial and indicating or counting mechanism, which may be of any suitable kind.
The spindle, 15, of the screw, 14, extends along the horizontal tube back beyond
the connection of the vertical tube, 20, and beneath the latter it has on it a worm
gearing with a wormwheel, 24, which is fast on a vertical spindle, 25, extending
up the tube, 20, to the indicator box, 23, at the top. With this modification the
revolutions of the screw, 14, are counted, and the number of revolutions shown
by the indicator in a given time serve as a datum for calculating the speed of
the ship.
The apparataus shown in figures 1 and 2, is not necessarily a fixture upon the
ship but can be removed at pleasure or be transferred from one ship to another.
In the modification shown in figures, 3, and 4, however a part of the apparatus is
shown as a fixture, and provision is made for projecting the main horizontal tube, 16,
outwards from the inside of the ship at a suitable depth below the water level. For
this purpose there is fitted at the side of the ship's stem, 18, (or it might be through
the stem itself) a pipe, 26, provided with a stop cock, 27, and with a stuffing
box, 28, and when the speed indicator is to be used its horizontal tube, 16, is passed
out through the pipe, 26. In this case only a short vertical pipe, 20, is required;
with the indicator box, 23, upon the top of it.
In the modification shown in figures, 11, and 12, the pressure of the water acts
directly on a ball, 29, on the front end of a spindle, 30, projecting forward from
and carried by the main horizontal tube, 16. A rack, 31, formed near the inner
end of the rod, 30, engages with a pinion, 32, on the lower end of a spindle, 33,
which extends up the vertical tube, 20, to the indicator box, 28, at the top, and at
the inner end of the rack, 31, there is a disc, 34, having holes through it and
which bears on a spring, 35, provided to resist the pressure on the ball, whilst
slite, 36, admit the water into the tube, 16, in order that the pressure due to the
depth at which the tube may be in the water shall not affect the indications. In
this modification it is difference of pressure (producing difference in the degree of
compression of the spring, 35) which is indicated and which serves as a datum for
calculating the speed of the ship.
In the modification shown in figures 5, 6, and 18, the direct pressure on the
front end of the main horizontal tube, 16, is transmitted through tubes by water
(or it might be partly by another fluid) to a mercurial siphon or U-tube, 37,
supported on gimbals on the deck or other convenient part of the ship. In the
front end of the main horizontal tube, 16, there is a cavity, 38, formed by a
partition or diaphragm and open at the front end to the water pressure, whilst a small
tube, 39, proceeds from the cavity, 38, back along the horizontal tube, 16, and up
more or less of the vertical tube 20, from which last it is continued in a flexible or
other suitable tube to one end of the mercurial siphon, 37. Behind the cavity, 38,
in the horizontal tube, 16, there is a chamber, 40, into which the water has access
by slits, 36, so that a pressure corresponding to the depth of the water acts in this
chamber and this pressure is communicated by a small tube, 41, proceeding from
the back of the chamber along the horizontal tube, 16, up the vertical tube, 20, and
thence to the other end of the mercurial siphon, 37. Pressures corresponding to the

page_text: depth of the water will thus act in both legs of the siphon, 37, and balance each
other, leaving any pressure caused by the forward motion of the ship to act alone
in one leg of the siphon. The pressure due to the motion will depress the mercury
in one leg of the siphon and raise it in the other and the difference of height of
the mercury in the two legs will correspond to the pressure due to the motion and
will serve as a datum for calculating the speed of the ship. Instead of the small
tubes, 89, 41, being in open communication with the cavity, 38, and chamber, 40,
in the main horizontal tube, 16, they may be filled with air and communicate with
bags filled with air and placed in the cavity, 38, and chamber, 40, the bags being
made of rubber or other suitable flexible and impermeable material. With such an
arrangement the pressures acting in the cavity, 88, and chamber, 40, will be
communicated by means of air to the mercurial siphon, 37.
With some modifications of my improved apparatus combined with suitable
clockwork the variations of the speed of a ship or the distance passed through by
the ship may be recorded.
Having thus particularly described my said Invention and the manner of
performing the same I have to state that I do not restrict myself to the precise
details herein described or delineated but that what I believe to be novel and
original and claim as the Invention secured to me by and in terms of the herein-
before in part recited Letters Patent is.
1. The fitting of apparatus for showing the speed of a ship, so as to project from
the bow of the ship with the part acted on in water which is not appreciably
disturbed, the parts of the apparatus being arranged and operating substantially as
herein before described.
2. The combination of parts substantially as hereinbefore described with reference
to figures, 1, 2, 7, 8, 9, and 10, of the accompanying drawings.
8. The combination of parts substantially as hereinbefore described with reference
to figures 11, and 12, of the accompanying drawings.
4. The combination of parts substantially as hereinbefore described with reference
to figures, 3, and 4, of the accompanying drawings.
5. The combination of parts substantially as herein before described with reference
to figures, 5, 6 and 18, of the accompanying drawings.
In witness whereof, I, the said Thomas Davison have hereunto set my hand
and seal this sixteenth day of August in the year of our Lord One thousand
eight hundred and eighty-two,
Witness
EDMUND HUNT
Patent Agent
Glasgow.
THOB. DAVISON. (LA)