Improvements in Apparatus for Measuring and Registering-the Speed of Vessels.
Year: 1893

page_text: Date of Application, 21st July, 1893
Complete Specification Left, 20th Apr., 1894-Accepted, 14th July, 1834
PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Measuring and Registering-the
Speed of Vessels.
We, EMILE RAVEROT of 1 Rue Boursault Paris, France, Electrician, and
PIERRE BELLY of 71 Quai d'Orsay, Paris, France, Mechanical Engineer, do
hereby declare the nature of this invention to be as follows:―
Our invention has reference to apparatus for measuring and registering the speed
of vessels-and it relates to the construction of a differential gauge or log the action
of which is in principle based upon the simultaneous employment of a Pitot's tube
and of a Darcy and Bazin's gauging tube. The invention consists in arrangements
whereby the hydraulic principle or action of these devices is adapted in connection
with suitable measuring and registering instruments for the purpose of measuring
and registering the speed of vessels.
The orientation of the orifices of the Pitot's tube and of the Darcy's gauging
tube relatively to the direction of the movement of the vessel through the water is
effected under determined conditions which are such that the difference of pressures
of the Pitot's tube and the Darcy's gauging tube is exclusively established by the
relative movement of the apparatus and of the liquid in which it is submerged
according to the formula of Torricelli v = 2gh; the speed of the vessel is thus
connected with the difference of pressure of the two tubes, g being the ordinary
coefficient of acceleration of gravity.
The pressures exerted in the gauging tube and in the Pitot's tube are transmitted
hydraulically to one or more differential manometric apparatus the kind of which
may vary with the type of vessel and her speed.
For craft of small speed difference of pressures is measured by the putting out of
level of two columns of water in glass tubes; a difference in height of about
1.35 metres is necessary for a speed of 5-15 metres per second or say 10 knots an
hour. For vessels of great speed a column of mercury is employed instead of
water in a U tube communicating hydraulically at the surface of its two branches
with the Pitot's and Darcy's tubes. The height of the readings therefore
corresponds with the displacement in the opposite direction of equal columns of
mercury of density A and of liquid of density & and the formula applicable to the
speed is v√2gh (A-8). A height of a metre corresponds approximately in
this case to a speed of 15.5 metres per second, say 30 knots an hour.
For permanent installation on board ship and in all cases the differential
manometric indication can be shown with advantage by a metallic Bourdon or Vidi
gauge specially arranged for differential use. In order that the elliptic tube of the
Bourdon gauge (or the flexible diaphragm of the Vidi gauge) may give the
indication of the differential pressure of the Pitot's tube and of the gauging tube
it is necessary--the interior of the Bourdon tube communicating with one of them-
that the other shall communicate with the medium in which this moves, that is to
say, with the box containing the Bourdon tube and this box must be liquid tight.
The differential indications given directly by the apparatus being sensitively
proportional to the pressures and consequently to the squares of the speeds, we
interpose a reducing mechanism (to give indications proportional to the speeds)
when the automatic registering of the indications of the instrument is to be effected
on a druin moved by clockwork. A daily diagram of the progress of the vessel is
thus obtained and the distance travelled between two given moments can be read
on the planimeter.
The hydraulic transmission of the pressures between the orifices of the Pitot's

page_text: and gauging tubes and the tubes of the indicating and registering devices is ensured
by completely filling the tubes with water or other liquid (glycerine or alcohol).
The hydraulic transmission of the pressures has the advantage of not altering
their differential value; the length and the small diameter of the transmitting
tubes allow of means being applied to prevent or diminish the oscillatious of the
liquid columns and this ensures the stability of the indications and readings. The
possible length of the transmission tubes between the orifices of the Pitot's and
Darcy's tubes and the indicating devices greatly assists the installation and permits
if necessary of placing the oriented orifices in an apparatus which the vessel tows,
connected by two flexible transmitting tubes. Preferably however the apparatus
is installed in the vessel; a smooth tube fitted with a sluice and a stuffing box is
placed below the water line. This tube serves to project to the outside the double
concentric tube having the Pitot's and Darcy's orifices. The tube proper is in the
centre and the gauging tube with lateral orifices is arranged concentrically; they
each communicate respectively with one of the two tubes which transmit the
differential pressure through the intermediation of a reservoir fitted with the
necessary cocks to ensure the complete hydraulic filling of the apparatus.
Dated this 21st dow of July 1802
J. C. MEWBURN,
55 & 56, Chancery Lane, London, Chartered Patent Agent.
COMPLETE
DILUIFICATION
Improvements in Apparatus for Measuring and Registering the
Speed of Vessels.
We, EMILE RAVEROT of 1 Rue Boursault, Paris, France, Electrician and
PIERRE BELLY of 71 Quai d'Orsay, Paris, France, Mechanical Engineer,
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 :-
Our invention has reference to apparatus for measuring and registering the speed
of vessels, and it relates to the construction of an apparatus the action of which is
in principle based upon the simultaneous employment of a Pitot's tube and a
Darcy and Bazin gauging tube. The methods or arrangements whereby the
principle or action of these tubes is adapted to the operation of a differential
manometric gauge or log for sea-going and other vessels form the subject of the
present invention.
Figures 1 to 5 of the annexed drawings represent a simple form given to a Pitot's
apparatus as improved by Darcy to render it capable of serving as a gauge or log
for speed tests corresponding to the extent of the scale of the pressure reading.
The two tubes shown in section in Figure 3 contain respectively the two orifices
which are the elements essential for the proper working of the apparatus; the one
of these orifices p is that of the Pitot tube, properly speaking, the other o is that
of the gauging tube. The axis of the orifice p is preferably horizontal and is so
arranged that the orifice points in the direction in which the vessel is moving; the
pressure resulting from this movement is transmitted to the liquid in the tube t;
the orifice o is on the contrary so situated that the pressure in the gauging or
equilibrium tube m remains practically independent of the movement.
These general relative positions and conditions of the orifices can moreover be
realized in any convenient manner; the difference of pressures in the Pitot tube
and in the gauging or equilibrium tube is determined by the relative movement of
the apparatus and of the liquid in which it is submerged according to the formula
of Torricelli v = k2gh; the speed is deduced from the formula, h being the
height of the liquid observed in the tube, g being the ordinary coefficient of
acceleration of gravity and k a const int always sufficiently approximate to unity,

page_text: the value of which should be determined by experience. The difference of
pressures established by the motion of the vessel between the Pitot and the gauging
or equilibrium tube is independent of the depth of immersion which is the same for
the orifices p and o.
The difference in pressure at
and o is transmitted to the special apparatus which
serve to measure and register it. In order to prevent the transmission of the great
variation of pressure we provide means to retard the immediate action of the
difference in pressure. This period of inertness depends on the length and diameter
of the double system of pipes.
In the apparatus shown in Figures 1 and 2 the measure of the speed corresponds
to the variation of the level of the liquid in two transparent tubes communicating
with each other at their upper part, where, by the intermediation of the tube R
provided with a cock, the air can be rarefied or compressed so as to regulate at
will the initial level of the water in the tubes. An accessory arrangement
(Figures 2, 4 and 5) consisting of a reading scale movable by means of a rack
along the tubes, completes this form of the apparatus; the level of the liquid in
the gauging or equilibrium tube falls during the progress of the vessel while that
in the Pitot tube rises in proportion to the elasticity of the air confined in the upper
part common to the two tubes.
The movable scale is graduated into metres (or feet) per second, kilometres (or
miles) per hour and knots per hour.
m
This form of apparatus is especially suitable for trials of small craft and vessels
of low speed because about 1-35 height of reading scale is required to indicate a
speed of 10 knots per hour (18 kilometres). In operation it is firmly fixed at the
bow of the vessel so that the tube provided with the orifices p and o may be
immersed ahead of the vessel and be set in the direction of its motion.
For trials of high speeds the form of apparatus shown in Figure 6 should be
employed in lieu of that just described; the indication is supplied by the variation
of level of a column of mercury confined in a U-tube the mercury in the two
branches being in hydraulic communication with the Pitot and Darcy tubes. (In
carrying out this arrangement the cock adjustments at the part containing the
mercury are made of metal which will not become amalgamated therewith,-for
example iron, steel, nickel &c.) The height of the readings then corresponds to
the displacement in contrary direction of equal columns of mercury of density A
and of water or other liquid of density o, and the formula of the instrument
is r : k√2gh (A—8). A differential pressure of a metre corresponds approxi-
mately in this case to a speed of 30 knots (55 kilometres) per hour, about 15.5 per
second. This indicator presents the great advantage of showing in absolute value
the measure of the differential pressure, and of permitting the direct determination
of the instrumental constant of the whole system employed. The reading of the
differential pressure is effected, as in the first form of indicator, from a movable
graduated scale.
m
For vessels of medium speed the indicator just described may be employed by
substituting bromoform for the mercury.
In all cases where our differential manometric log is intended not only for
temporary trials, but for permanently indicating and registering speed, the complete
installation on board ship includes several parts which we will now describe:
A bored tube A (Figure 7) provided with a stuffing box L is fitted below the water
line in front of the vessel. The tube F (Figures 7, 8, 8 bts and 8ter) is projecte:
through the tube A into the water outside the vessel (or the complete metallic
piece F shown in detail in Figures 14 to 18) the said tubes being provided with the
orifices p and o. The tube A may be disposed horizontally following the axial line
of the vessel, through the stem for example, as indicated in Figure 7; it then
gives passage to the tubes F disposed concentrically as shown in detail in
Figures 8, 8bts, 8ter; the situation of the orifices p and o is also detailed in these
figures. The inner tube with its central hole p fulfils the office of the Pitot tube,

page_text: the concentric tube with its lateral orifice o that of the gauging, or equilibrium
tube. The bored tube A is also provided with a screw down valve or gate K for
closing it, when the tube F is not in position.
When on the contrary the form of the front of the vessel is not adapted for
such a disposition the bored tube A may occupy a position transverse to the axis of
the vessel (Figure 14) and give passage to a compound metallic piece F the lower
immersed portion of which carrying the orifices p and o offers by reason of its form
little resistance to the progress of the vessel; Figures 15 and 16 show the form of
the piece F circular at its upper and ogival at its lower part, and Figures 17 and 18
show in section the detail of the lower extremity and its orifices p and o. In both
cases each of the orifices p and o communicates independently by a cock, joints and
an intermediate metallic tube with the central part of a reservoir situated below
the water line. The two reservoirs I and I' (Figure 9), placed at the same level,
have each at top a blow-off cock 9 and are connected hydraulically to one of the.
branches of the manometric apparatus for indicating and registering, by means of
joints and a metallic tube. In the first place the tubes T and M are connected
with the top of the transparent branches of the U-tube (Figure 6-mercury or
bromoform apparatus) an arrangement which we expressly state should be employed
concurrently with the other arrangements the graduation of which it serves to
establish or control.
Figure 10 shows further the connection of the tubes T and M with an indicating
apparatus and with a registering apparatus because of the particularities which
the differential operation on the one hand and the nature of the indications to be
registered on the other, introduce into their construction.
In order that a Bourdon metallic tube (or a Vidi flexible diaphragm) may furnish
the indication of the differential pressure in the tubes T and M it is necessary, the
interior of the Bourdon tube (Figure 11) communicating with one of them-M for
example-that the other shall communicate with the medium in which this moves,
that is to say with the metallic box containing the Bourdon tube, the stanchness
of which must be assured. With this object the spindle carrying the needle or
pointer of the instrument may for example pass through a stuffing box g, Figure 12.
The indications furnished directly by such a Bourdon gauge (indicator D
Figure 10) being proportional to the pressures and consequently to the squares of
the velocities there is interposed in the mechanism of the registering apparatus E
(Figures 10 and 11)-either the differential registering apparatus of Bourdon or
the special differential registering apparatus of Richard-a so-called Richard
cam ff which will reduce the movements of the equilibrated registering lever s
to simple proportion to the velocity. A registering drum H having a clockwork
movement suffices to take up a daily diagram of the progress of the vessel and
from this diagram the distance travelled by the vessel between any two given times
may be read by means of a planimeter.
The hydraulic transmission of the pressures from the operating orifices to the
indicating and registering mechanism offers the advantage of not altering the
differential value of same; in order to assure it it suffices to previously completely
fill the tubes with either water alone or with water and another liquid of slightl
greater density (such as benzoate of methyl, C.HO₂; salicylate of methyl,
CHO glycerine, C,H,O3; or bromated benzine CH,Br).
8
8
The cocks n and n' serve to fix the initial level of the liquid of transmission ia
the intermediate reservoirs, and the blow-off pieces, such as jj', with which all the
apparatus are provided, permit of the complete expulsion of air from the double
transmission conduit T and M during the refilling process.
The operation of the apparatus is as follows:-
The pressure at the orifice p of the Pitot tube is transmitted to the tubet,
reservoir I, tube T and its ramifications; in the same way the pressure at the
orifice o of the gauging or equilibrium tube is transmitted to the tube m, reservoir I',
tube M and its ramifications; the difference of the pressures exerted operates the
mechanisms, indicator D, registering apparatus E and differential manometer U.

page_text: Besides serving for the refilling operation the reservoirs I and I are intended to.
retain and remove the bubbles of air which may be occasionally introduced through
the fittings. In order that sudden variations of pressure which may be produced
correlatively shall not produce dangerous shocks upon the mechanism of the
indicator and registering apparatus, it is provided that the tubes T and M shall,.
owing to their length and small diameter, introduce into the oscillations of the
liquid columns a period of inertness of sufficient duration. The introduction of
this period of inertness in the stability of the indications and readings furnished
by our differential manometric log is important when employed at sea.
The length of the tubes T and M is of great advantage as it allows of the
instruments, Figures 6 and 10 being placed at an easily accessible part of the
vessel. It permits also of using the tubes, Figures 8, 8bts and 8ter as part of a drag
log (Figure 13) connected hydraulically to the vessel by two flexible tubes accom-
panying and forming part of the towing cable; these flexible tubes take the place
of the tubes m and t, Figures 7 and 9, and are connected on the vessel to the
intermediate reservoirs.
These measuring and registering apparatus are readily capable of being so
adapted as to produce repetitions of their indications by any ordinary electrical
means.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what
we claim in respect of apparatus for measuring and registering the speed of
vessels is :-
1. The several arrangements of measuring and registering apparatus substan-
tially as hereinbefore described, the action of which is in principle based upon the
simultaneous employment of a Pitot tube and a Darcy tube as set forth.
2. The simultaneous employment of a Pitot tube and a Darcy tube (or equivalent
equilibrium tube), in combination with a mercury gauge, a bromoform gauge or a
Bourdon (or Vidi) gauge, specially arranged for the differential operation, sub-
stantially as hereinbefore described.
3. The differential operation of a Bourdon, Vidi or other gauge actuated by
Pitot and Darcy's elementary tubes, and provided for the purpose of registering
the speed with a cam for assuring simple proportion to the velocity, substantially
as hereinhefore described.
4. The application of exclusively hydraulic transmission in the entire apparatus.
and the use of the liquids of transmission hereinbefore mentioned as set forth.
5. The employment of blow-off devices to allow of the independent and complete
hydraulic refilling of the Bourdon tube and the hermetically closed box in which
it works as hereinbefore described.
6. The particular arrangement of tubes provided with Pitot and Darcy elementary
orifices as herein before described.
7. The removable arrangement of the tubes or of the metallic piece carrying.
the orifices (p and o) in a bored tube passing through the vessel below the water
line and provided with a valve and stuffing box, substantially as hereinbefore
described.
8. The means whereby a period of inertness as hereinbefore described is
obtained, that is to say by the length and small diameter of the liquid columns
which transmit the pressures, in order to assure sufficient stability of the indications
and readings as set forth.
9. In apparatus such as herein before described the employment of intermediate
reservoirs, substantially as and for the purpose set forth.
Dated this 20th do of A1 1004
J. C. MEWBURN,
55 & 56, Chancery Lane, London, Chartered Patent Agent..