IMPROVE- MENTS IN WATER PRESSURE SPEED INDICATORS
Year: 1871

page_text: LETTERS PATENT to James Robert Napier, of Glasgow, in the County
of Lanark, North Britain, Engineer, for the Invention of " IMPROVE-
MENTS IN WATER PRESSURE SPEED INDICATORS."
Sealed the 9th April 1872, and dated the 18th October 1871.
PROVISIONAL SPECIFICATION left by the said. James Robert Napier
at the Office of the Commissioners of Patents, with his Petition,
on the 18th October 1871.
I, JAMES ROBERT NAPIER, of Glasgow, in the County of Lanark,
North Britain, Engineer, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN WATER PRESSURE SPEED INDICATORS," to
be as follows, that is to say :-
-
This Invention relates to speed indicators of the kind in which the
relative velocity of water and a solid as, for example, of a ship, or of a
current; is indicated by the difference of height between the columns of
mercury in a shaped glass tubo, to the legs of which pipes are
connected terminating in the water. And the object of the Invention

page_text: is to simplify and render more convenient the means for removing
the air.
The Invention consists according to one modification in making a
connecting passage above the mercury between each leg of the U tube,
and the sides of a chamber having a discharge pipe at its lower part, and
in fitting in this chamber a conical plug capable of being turned by an
external handle. In one position of the plug it closes both the side
passages into the chamber; but on being turned about one-quarter
round it causes one of the side passages to communicate with a bore in
the plug, entering at its side and terminating in a central nozzle at its 1
lower end, whilst the other passage communicates with a cavity in the
side of the plug, giving access round the central nozzle to the discharge
pipe at the lower end of the plug chamber. The discharge pipe extends
downwards as far as conveniently practicable; in steamboats its lower
extremity may be connected with the condenser or with the feed or
other engine pump. The precise arrangement of parts may be modified
so long as the pipe connected to one of the legs of the U tube is arranged
to induce a current or flow through the pipe connected to the other
leg.
The Invention consists according to another modification in making a
passage above the mercury between the legs of the U tube, and which
can be opened or shut by means of a stop-cock, so that when a current
flows from one of these pipes through the stop-cock it forces the air
before it through and out of the other pipe.
SPECIFICATION in pursuance of the conditions of the Letters Patent, 2
filed by the said James Robert Napier in the Great Seal Patent
Office on the 17th April 1872.
TO ALL TO WHOM THESE PRESENTS. SHALL COME, Į, James
ROBERT NAPIER, of Glasgow, in the County of Lanark, North
Britain, Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by. Her
Letters Patent, bearing date the Eighteenth day of October, in the
year of our Lord One thousand eight hundred and seventy-one, in
8

page_text: 6
Figure 1 is a front elevation of a modification of my improved water
pressure speed indicator or 'pressure log" as made for indicating the
speed of a ship, and in it a U shaped glass tube 1, 2, with mercury
in it is used for indicating the pressure; Figure 2 is a vertical section of.
the upper part.
The mode in which the mercury is acted on by the difference of
pressure in the two legs 1, 2, of the U tube, and shows the speed of a
-ship or current, is known and need not be here minutely explained.
The tops of the U tubo 1, 2, are fixed in a metal head piece 3, in which
are also fixed the tops of two outer tubes 4, 5, and a middle tube 6; and
cross passages are made in the head piece, such that one outer tube 4 is
always in communication with one leg 1 of the U tube, and the other
outer tube 5 is always in communication with the other leg 2 of the
U tube. These outer tubes 4, 5, are connected with the usual pressure
nozzles placed so as to be suitably acted on by the water outside of the 1
ship, and they are made of glass so that it may be seen when thero is
any air in them, or when from leakage in the pipes or connections air
passes up them on water being run through them.
For the convenient removal of the air, which is the principal object
of my present Invention, I use a conical plug 7, Figure 2, which is
carefully fitted into a conical chamber formed in the head pieco 3, being
held in by a screw gland 8, and being fitted with a handle 9 to turn
it by. Passages from the tops of the U tube 1, 2, lead into opposite
sides of the plug chamber, but are closed by the plug 7, when this is
turned about a quarter round from the position in which it is shown in
Figure 2. The plug 7 is formed with a radial passage leading into an
axial passage, and when the plug is in the "open" position as shown in
Figure 2, the radial passage in it is in communication by the passage in
the head piece with the leg 1 of the U tube. A channel is formed in
the side of the plug opposite to the radial passage, and when the plug is a
in the open position, makes a communication from the top of the other
leg 2 of the U tube, through the passage in the head piece 3 to the
lower part of the plug chamber. The axial passage in the plug
terminates in a nozzle at the bottom end of the plug, this nozzle being
considerably smaller than the body of the plug, and being surrounded 3
by a conical space forming the lower part of the plug chamber. The
bottom of the plug chamber communicates with the middle tube 6 by
an entrance near the end of the plug nozzle, and at the entrance the

page_text: tube 6 has an internal diameter slightly greater than that of the nozzle,
the diameter gradually increasing downwards until it is from three to
four times that of the nozzle. The middle or discharge tube 6 is
extended downwards as far as convenient; in steamboats its lower
extremity may be connected with the condenser, or with the feed or
other engine pump. In Figure 2 the plug 7 is shown in the open or
communicating position, and when it is in this position any air in the
tubes 1, 2, 4, 5, will pass off by the middle tube 6, the current flowing
from the tube with greater pressure causing the requisite flow from that
with less pressure.
The arrangement and conformation of the parts as shown in Figures 1
and 2 may be modified so long as the pipe connected to one leg of the
mercury tube or equivalent part is arranged to cause a current or flow
through the pipe connected to the other leg.
Another modification of my Invention as applied in connection with. a
mercury tube consists in making a passage above the mercury between
the legs 1, 2, of the U tube, and which can be opened or shut by means
of a stop-cock, so that when a current flows from one of these pipes
through the stop-cock it forces the air before it through and out of the
other pipe.
It is the vertical heights of the mercury in the U tube 1, 2, which
indicate the speeds, and the apparatus may be hung in gimbals when
used on a ship, so as to be as little as possible affected by any rolling or
other angular motion of the ship. I however prefer to have the apparatus
fixed to a fore-and-aft bulkhead or other convenient part of the ship, and
to apply near it fixed to a cross bulkhead a dial 10, and correcting
pendulum index 11. The dial 10 is fixed, and has drawn on it a series of
different circles with their centres all in the same line 12-12, which is
vertical when the ship is so, but which is shown inclined in Figure 2, to
correspond to a supposed inclination of the ship. The tops of the circles
all pass through the same point on the line 12-12, and through this
point is made to pass the axis of motion of the pendulum index 11,
which is hung from a bracket or stud 13. The pendulum index 11 is
fitted with a weight.14 applied very near its axis of motion, so as to
make its oscillation period very short, and so as to enable it to maintain
a nearly vertical position notwithstanding the angular motion of the
ship. To use this correcting dial and index the position of the top of
the mercury in the tube 2. as shown on the scale beside that tube, is

page_text: observed, and the corresponding circle on the dial 10 is followed to the
point where it crosses the left-hand edge of the index rod 11, and that
point measures on the rod 11 the true vertical height of the mercury,
and consequent correct speed of the ship.
Figures 5 and 6 are vertical sections as at right angles to each other
of a modification of the water-pressure speed indicator, in which two
Bourdon gauge tubes 15, 16, are used for showing the pressure, theso
gaugo tubes being fixed into the head piece 3, in place of the two legs
1, 2, of the U tube of the modification shown in Figures 1 and 2, and
hcrcin-before described, the means for removing air remaining the same.
The free ends of the tubes 15, 16, are connected by links 17, 18, to levers
19, 20, on a spindle 21, and this spindle has fast on it a toothed sector 22,
gearing with a pinion 23, on the spindle of an index 24, which shows
the speed on a dial 25. The tubes are connected to the spindle 21 in
such a way that a diminished pressure in one tends to turn the spindle
in the same direction as an increased pressure in the other, whilst on any
increase or decrease of pressure taking place equally in both tubes from
change in the depth of immersion of the outside pressure nozzles or
otherwise, one tube counteracts the other, and no alteration of the index
follows. The tubes 15, 16, are filled with water.
Figures 7 and 8 are vertical sections as at right angles to each other
of a modification in which only one Bourdon gauge tube 15 is used; but
whilst the inside of this tube is filled with water and put in com-
munication by the pipe 4 with one of the outside pressure nozzles, its
outside is subjected to the pressure in the pipe 5 communicating with
the other outside pressure nozzle, this pipe 5 being made to open into
the casing 26, containing the gauge tube 15, which casing is consequently
filled with water when the apparatus is in working order. The gauge
tube 15 is fixed into the head piece 3, and the interior of the casing
communicates therewith by an opening 27 at its top. The index
mechanism is fitted to work in the water, the position of the index 21
being visible through the glass cover 28, on which the scale is marked.
The application of my improved appliances for removing air from the
water pressure speed indicator admits of the indicator being conveniently
placed in a bigher position on board a ship than that of the water level;
but the precise height at which it can be placed will depend upon the
special cucumstances of each case.

page_text: 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
the herein-before in part recited Letters Patent is,-
1. The arranging or combining together of the parts of water-pressuro
speed indicators, substantially in the improved modes herein described
and delineated.
2. The fitting of water-pressure speed indicators with appliances for
removing air, substantially such as are herein-before described.
In witness whereof, I, the said James Robert Napier, have hereunto
set my hand and scal, this Sixteenth day of April, in the year of
our Lord One thousand eight hundred and seventy-two.
5 Witness,
EDMUND HUNT,
Patent Agent,
Glasgow.
JAMES R. NAPIER. (L.S.)