Improvements in Ship-logs and Current-meters.
Year: 1887

page_text: Date of Application, 23rd May, 1887
Complete Left, 23rd Feb., 1888
Complete Accepted, 23rd Mar., 1888
[Communicated from abroad by PETER KRISTIAN PRYTZ, Professor of Physics at the
Technical Institute, and GEORGE ADOLPH RUNG, Sub Director of the Meteoro-
logical Institute, both of the City of Copenhagen, Denmark.]
Improvements in Ship-logs and Current-meters.
I CHARLES ALFRED ADOLF CAPITO Civil Engineer of 63, Queen Victoria Street in
the City of London, do hereby declare the nature of this invention to be as
follows:-
The object of this invention is to measure, and to continuously indicate, and to
record if required, the speed of a vessel through the water or the velocity of a stream,
but it may be applied to other purposes to which the principle is applicable.
For the purpose of this invention I place at a convenient depth below the surface
of the water two pipes, one bent so that the orifice faces the direction in which
the vessel is going, or faces the stream, and the other pipe bent so that the orifice faces
the opposite direction to the orifice of the first pipe.
The said orifices are by preference placed at the same depth below the surface of
the water.
At the orifice of the first pipe pressure bearing a certain ratio to the velocity of the
vessel or the stream will be produced, and in the second pipe a partial vacuum also
bearing a certain ratio to the velocity of the vessel or the stream will be produced.
There will also be in both of the aforesaid pipes in addition, the hydro-static pres-
sure due to the depth below the surface of the water to which they are immersed, but
as this will be the same in each pipe the difference between the pressure at the orifices
of the two aforesaid pipes will bear a given ratio to the velocity of the vessel or the
stream independent of the depth to which they are immersed, and variations in depth
such as would take place on a vessel will not affect the result.
To measure the difference between the pressures at the orifices of the two aforesaid
pipes I cause air to be forced, by means of a pump or other suitable apparatus, into
each pipe, of sufficient pressure to overcome the respective pressures in each pipe, but

page_text: in so small a quantity as to only slowly bubble out of the orifices of the pipes. The
air in the respective pipes will thus be always at the pressure caused by the velocity
of the vessel or the stream plus the aforesaid bydro-static pressure.
To indicate the difference of pressures at the orifices of the aforesaid pipes, I
provide a glass-tube bent in the form of a U and connect one end of the said glass-
tube with one of the aforesaid pipes and the other end of the glass-tube with the
other of the aforesaid pipes and place mercury or some other suitable fluid in the said
bent glass-tube. The difference in pressure will be indicated by the position of the
mercury or the fluid.
Instead of the U-formed glass-tube I may use any other suitable differential
pressure-gauge. As there is only a very slight motion of the air in the tubes
connecting the indicators or gauges with the two aforesaid pipes, the indicators may
be a considerable distance from the pipes and there may be as many of them as may
be found convenient.
The velocity of the vessel or the stream may be calculated from the pressures
indicated, or it is obvious that the indicators may be graduated to show such velocity
direct.
The apparatus will also indicate the direction of the motion of the vessel or the
stream as the mercury or fluid will rise up one side or the other of the bent glass-tube
in accordance with the direction, and the gauge-hand will revolve in one direction
or the other in like manner. One apparatus may also be made self-recording.
I may also apply only one pipe, placed at a convenient depth below the surface of
the water, but in such a manner that the orifice of the aforesaid pipe is kept at a
constant depth below the surface of the water, which can be done, for instance, by
fixing the aforesaid pipe to a float.
The pressure at the orifice of the pipe will be the pressure due to the velocity of
the vessel or the stream in addition to the hydro-static pressure of the water above
the orifice which latter pressure would in this case be constant.
The pressure at the orifice of the aforesaid pipe is also measured here by forcing a
slow current of air through the pipe. As indicators I use pressure or vacuum-gauges
of any suitable construction.
Datel
1 1
1007

page_text: COMPLETE SPECIFICATION.
Improvements in Ship-logs and Current-meters.
I CHARLES ALFRED ADOLF CAPITO Civil Engineer of 63, Queen Victoria Street
in the City of London do hereby declare the nature of this invention and in what
manner the same is to be perforined, to be particularly described and ascertained in
and by the following stateinent :-
The object of this invention is to measure, and to continuously indicate, and to
record if required, the speed of a vessel or any other body through the water or any
other liquid, or the velocity of a stream, or the amount of liquid passing through a
pipe, and it may be applied to other purposes to which the principle is applicable.
For the purpose of this invention I place, as shown in Fig. I. of the accompanying
drawings, at a convenient depth below the surface of the liquid two pipes pand
which continue outside the liquid by pipos q and g¹ which again are connected by
pipes and with a pipe t.
I also connect one or more indicators I and I2 with the pipes 7 and 7'. The afore-
said pipes p and pl are bent below the surface of the liquid so that their orifices m
and m face, opposite directions, but are always placed so that one of the orifices faces
the direction in which the liquid or the pipes p and p' are moving.
Both these orifices are by preference placed at the same depth below the surface of
the liquid.
Suppose the liquid is moving in the direction indicated by the arrow Fig. 1, or
the
pipes p and pare moving in the opposite direction of the said arrow,
then a
pressure at the orifice m, bearing a certain ratio to the velocity of the liquid or that
of the pipes p and pl, will be produced, and in the pipe p₁ a partial vacuum, also
bearing a certain ratio to the velocity of the liquid or that of the pipes p and p', will
be produced.
There will also be in both of the pipes pand pl, in addition, the hydro-static
pressure due to the depth below the surface of the liquid to which the orifices m
and mare. immersed, but as this hydro-static pressure will be the same in each pipe,
the difference between the pressures at the orifices m and m will bear a given ratio
to the velocity of the liquid or that of the pipes p and pl, independent of the depth
to which they are immersed, and variations in depth, such as would take place on a
vessel, will not affect the result.
I
To measure the difference between the pressures at the said orifices m and m³,
cause air or any suitable gas to be forced through a pipe t, by means of a pump or
other suitable apparatus, into each of tho pipes p and pl, but in so small a quantity as
to only slowly bubble out of the orifices m and m¹. The air or gas in the respective
pipes will thus be always at the pressure caused by the velocity of the liquid or that
of the pipes p and p', plus the aforesaid hydro-static pressure due to the depth of the
orifices m and m¹ below the surface of the liquid. I apply a tap to each of the
pipes and in order to regulate the amount of air or gas to pass through the pipes.
Instead of these taps I may use any other suitable apparatus for regulating the said
2'

page_text: amount of air or gas, such as valves. To indicate the difference of pressure at the
orifices m and m¹, I may use as shown in Fig. 1. a glass-tube bent in the form of a U
and connect its two open ends with pipes and q¹ respectively, and fill it partly with
mercury or some other suitable fluid. The difference in pressure will be indicated or
measured by the position of tlie mercury or the fluid.
Instead of the U-formed glass-tube I may use any other suitable differential gauge
such as I Fig. 1. This indicator is constructed in a similar way as a Schäffer-gauge,
but it is made air-tight on both sides of the diaphragm.
As there is only a very slight motion of the air or gas in the pipes ", ¹, q, q',
p and p¹, the indicators may be at a considerable distance from p and p¹, and there
may be as many of them as may be convenient.
The velocity of the liquid or that of the pipes p and p' may be calculated from the
pressures measured, or it is obvious that the indicators may be graduated to show
such velocity direct.
The apparatus will also indicate the direction of the motion of the liquid or that of
the pipes p and p, as the mercury or the fluid in I will rise up one side or the other
in accordance with the direction, and the gauge-hand of 12 will revolve in one direction
or the other in like manner. The indicator may also be made self-recording. In this
case it is constructed on the principle of the self-recording aneroid-barometer. The
gauges may be made to indicate according to requirements and application: knots
hour;
per
feet per second gallons per minute; revolutions per minute (in case it is
used to measure the number of revolutions, for instance, of a turbine); etc.; etc.
When the apparatus is applied as a Ship-log, the pipes p and p will usually be
fixed to the ship through a hole in the same, but in such a manner that they can be
drawn in for cleaning.
As shown in Fig. 2. of the accompanying drawings, I may in some cases apply
only one pipe p, placed at a constant depth below the surface of the liquid, which can
be done, for instance, by fixing the aforesaid pipe p to a float. The pressure at the
orifice m will be the pressure due to the velocity of the liquid or that of the pipe p, in
addition to the hydro-static pressure of the liquid above the said orifice, which latter
pressure would in this case be constant. The pressure at the orifice m is also
measured by forcing a slow current of air or gas through the pipes r, q and p in a
similar way as explained above. The apparatus in this form will also show the direc-
tion of the motion of the liquid or that of the pipe p. Indicator I Fig. 2. is a
U-formed glass-tube partly filled with mercury or some other suitable fluid, the one
end is open to the atmosphere. Indicator I is constructed as an ordinary Schäffer-
gauge. As indicator I may use any suitable pressure or vacuum-gauge. I may also
use a self-recording indicator constructed on the principle of the self-recording
aneroid-barometer.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
1. The application for measuring and indicating the velocity of a vessel or other
body through a liquid, or the velocity of a stream, by forcing a slow current of air or
gas through two pipes p and p¹ Fig. 1. or through one pipe p Fig. 2 in connection
with one or more pressure, differential or vacuum gauges substantially as herein
described and shown.
Dated this 92nd day of February 1888