IMPROVEMENTS IN GAUGES PROVISIONAL SPECIFICATION
Year: 1875

page_text: LETTERS PATENT to John Townsend Bucknill, of the War Office,
Whitehall, Lieutenant in Her Majesty's Corps of Royal Engineers,
and Louis Paschal Casella, of Holborn Bars, London, Scientific
Instrument Maker, for the Invention of "IMPROVEMENTS IN GAUGES
PROVISIONAL SPECIFICATION left by the said John Townsend
Bucknil and Louis Paschal Casella at the Office of the Com-
missioners of Patents, with their Petition, on the 4th August
1875.
WC, JOHN TOWNSEND BUCKNILL, of the War Office, Whitehall,
Lieutenant in Her Majesty's Corps of Royal Engineers, and LOUIS
PASCHAL CASELLA, of Holborn Bars, London, Scientific Instrument
Maker, do hereby declare the nature of the said Invention for "IM-
PROVEMENTS IN GAUGES FOR INDICATING FLUID PRESSURES," to be as follows:-
In order to prevent violent fluctuations of the indicating arm of any
pressure gauge subjected to severe shocks or to sudden alterations in the
-

page_text: pressure of the fluid which has to be indicated, and consequently in
order also to enable a reliable reading to be obtained from either a
maximum or a minimum reader or hand which may be employed in
such gauges, we fix a small cylinder filled with a stable liquid, such as
glycerine. In the case of the instrument and in this cylinder we place
a piston provided with a small hole or small holes or which fits the
cylinder loosely, and we connect the piston rod with some convenient
moving portion of the pressure gauge by a suitable mechanical arrange-
ment; for instance, by a rack upon the piston rod gearing with a pinion
on the axis of the indicating arm. The movement of the indicating arm
is thus controlled by the flow of the liquid past the sides of or through
the hole or holes in the piston. This can be arranged in other manners,
for instance, the piston can fit the cylinder, and a small hole or small
holes can be made in a cover at one end of the cylinder, or the piston
rod can pass through a hole in the cylinder cover slightly larger than
itself. In either case outside the cylinder cover a chamber is provided
for the reception of the liquid forced out of or drawn into thic cylinder
by the movement of the piston, and this chamber is so arranged that
the glycerine is brought back by the return movement of the piston.
The employment of a liquid in combination with a piston working
in a cylinder, as herein-before described, is applicable to pressure gauges
generally.
In order to effect similar results without using the piston and cylinder,
we sometimes fix a fan or fans to some of the moving parts of a pressure
gauge, such as the indicating arm or its spindle; we fill the pressure
gauge with a transparent and stable liquid, such as glycerine; we
divide the interior of the pressure gauge into compartments, so that the
liquid will partake of any movement given to the body of the gauge.
Or in order to effect similar results we sometimes balance the moving
parts, and this may be done, for example, by employing two racks, one
at each side of a pinion on the spindle of the indicating arm, so that in
case the instrument receives a severe shock they act as compensators
one to the other.
We fill the instrument with liquid as before, and sometimes we fix a
plate or disc across the ends of the racks for the purpose of offering
resistance to their movement through the liquid.
The employment of a fan or fans and of a liquid or of two racks and

page_text: a liquid as described, is applicable to pressure gauges generally, but we
prefer the arrangements in which a liquid is employed in combination
with a piston working in a cylinder as before described.
The fan or fans and the piston and cylinder arrangement, or the two
racks and the piston and cylinder arrangement can however be combined
in the same instrument.
The foregoing improvements have been invented by us with a view to
obtain instruments that would give reliable indications of pressure in
fluids when the said instruments are subjected to sudden shocks or to
very sudden variations in the fluid pressure, erroneous readings due to
the vis viva and inertia of the moving parts being climinated by the
controlling action of the apparatus herein-before described.
The pressure gauge which we prefer to use under such conditions is
constructed as follows:-A metal case with a glass face is nearly filled
with a transparent and stable liquid, such as glycerinc, a small air
chamber being provided whose capacity is somewhat greater than that
of a cylinder, the outer end of which is covered with a thin elastic
diaphragm, and which is connected with the fluid whose pressure it is
required to indicate. A piston fits this cylinder accurately and rests
against the diaphragm. The hole in the cylinder cover through which
the piston rod is taken is made slightly larger than the rod, and the
piston rod which works in suitable guides is connected to the indicating
arm of the gauge by means of a rack and pinion as before described.
A maximum indicator is actuated in one direction only by the indicating
arm, and is set by hand at zero by means of a set rod passing through a
stuffing box fixed either in the centre of the glass face or in the side of
the case, in which latter position bevil gearing is necessary. The set rod
is provided with a key or button either moveable or fixed to the rod.
The piston is pressed against the diaphragm by a spiral spring, the
pressure being gradually increased by the compression of the spring, as
the piston and diaphragm are forced in by an increasing external
pressure.
The action of the gauge can be readily understood by referring to the
description of a similar arrangement herein-before given.
We consider it important that the spring employed in this and other
pressure gauges to resist the pressure of the outer fluid should be a
sprial spring surrounding the piston rod and formed from an uniform

page_text: steel wire, as we have found by experiment that other forms of spring
as at present made cannot be depended upon to act uniformly.
The foregoing improvements have been made by us during a course of
experiments carried on with a view to obtain an instrument for
measuring the depth of the sea by means of pressure. Any such
instrument must be subject to severe blows and yet must record the
greatest pressure to which it is subjected with exactitude. The gauge
we employ for this purpose is that last described, and in order to adapt
it for such work we simply increase the strength of the case and of the
glass face, the set rod for the maximum reader being taken through the
side of the case and bevil gearing employed as before described. This
gauge when sunk in the sea by means of a lead to any, up to a certain
depth, will on being brought to the surface record the greatest pressure
to which it has been subjected, and from this record the depth to which
the gauge sank can be ascertained, or the dial can be graduated so that
this depth can be read off at once.
It is part of our Invention independently of any particular arrange-
ment for controlling the moving parts of the instrument to employ an
elastic diaphragm, and to fill such portion or portions of the gauge
inside such diaphragm to which it may be wished to carry the external
fluid pressure with a transparent and stable liquid, such as glycerine, we
thus prevent the external fluid entering the gauge.
SPECIFICATION in pursuance of, the conditions of the Letters Patent,
filed by the said John Townsend Buckmill and Louis Paschal
Casella in the Great Seal Patent Office on the 4th February
1876.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, JOHN
TOWNSEND BUCKNILL, of the War Office, Whitehall, Lieutenant in Her
Majesty's Corps of Royal Engineers, and LOUIS PASCHAL CASELLA, of
Holborn Bars, London, Scientific Instrument Maker, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fourth day of August, in the year of
our Lord One thousand eight hundred and seventy-five, in the thirty-
ninth year of Her reign, did, for Herself, Her heirs and successors,

page_text: give and grant unto us, the said John Townsend Bucknill and Louis
Paschal Casella, Her special licence, that we, the said John Townsend
Bucknill and Louis Paschal Casella, our executors, administrators, and
assigns, or such others as we, the said John Townsend Bucknill and
Louis Paschal Casella, our executors, administrators, and assigns, should
at any time agree with and no others, from time to time and at
all times thereafter during the term therein expressed, should and law-
fully might make, use, exercise, and vend, within the United Kingdom
of Great Britain and Ireland, the Channel Islands, and Isle of Man,
an Invention for "IMPROVEMENTS IN GAUGES FOR INDICATING FLUID PRESSURES,"
upon the condition (amongst others) that we, the said John Townsend
Bucknil and Louis Paschal Casella, our executors or administrators, by
an instrument in writing under our, or one of our or their, or one of
their hands and seals, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be
performed, and cause the same to be filed in the Great Seal Patent
Office within six calendar months next and immediately after the date
of the said Letters Patent.
NOW KNOW YE, that we, the said John Townsend Bucknill and
Louis Paschal Casella, do hereby declare the nature of our said Inven-
tion, and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following state-
ment thereof, reference being had to the accompanying Drawings, that
is to say :-
In order to prevent violent fluctuations of the indicating arm of any
pressure gauge subjected to severe shocks or to sudden alterations in the
pressure of the fluid which has to be indicated, and consequently in order
also to enable a reliable reading to be obtained from either a maximum or
mininum reader or hand, which may be employed in such gauges, we fix
a small cylinder filled with a stable liquid, such as glycerine, in the case
of the instrument, and in this cylinder we place a piston provided with a
small hole or small holes, or which fits the cylinder loosely, and we
connect the piston rod with some convenient moving portion of the
pressure gauge by a suitable mechanical arrangement, for instance, by a
rack upon the piston rod gearing with a pinion on the axis of the indi-
cating arm. The movement of the indicating arm is thus controlled by
the flow of the liquid past the sides of or through the hole or holes in the
piston. This can be arranged in othermanners, for instance, the piston

page_text: can fit the cylinder, and a small hole or small holes can be made in a
cover at one end of the cylinder, or the piston rod can pass through a
hole in the cylinder cover slightly larger than itself. In either case
outside the cylinder cover a chamber is provided for the reception of the
liquid forced out of or drawen into the cylinder by the movement of the
piston, and this chamber is so arranged that the glycerine is brought
back by the return movement of the piston.
The employment of a liquid in combination with a piston working
in a cylinder, as herein-before described, is applicable to pressure gauges
generally.
In order to effect similar results without using the piston and cylinder
we sometimes fix a fan or fans to some of the moving parts of a pressure
gauge, such as the indicating arm or its spindle; we fill the pressure
gauge with a transparent and stable liquid, such as glycerine, and we
divide the interior of the pressure gauge into compartments, so that the
liquid will partake of any movement given to the body of the gauge. Or
in order to effect similar results we sometimes balance the moving parts,
and this may be done, for example, by employing two racks, one at cach
side of a pinion on the spindle of the indicating arm, so that in case the
instrument receives a severe shock they act as compensators onc to the
other.
We fill the instrument with liquid as before (or the liquid may be
omitted), and sometimes we fix a plate or disc across the ends of the
racks for the purpose of offering resistance to their movement through
the liquid.
The employment of a fan or fans and of a liquid or of two racks and a
liquid, as described, is applicable to pressure gauges generally, but we
prefer the arrangements in which a liquid is employed in combination
with a piston working in a cylinder as before described.
The fan or fans and the piston and cylinder arrangement, or the two
racks and the piston and cylinder arrangement, can however be combined
in the same instrument.
The foregoing improvements have been invented by us with a view to
obtain instruments for measuring the depth of the sea by means of
pressure, or that would give reliable indications of pressure in fluids. 3
when the said instruments are subjected to sudden shocks or to very

page_text: sudden variations in the fluid pressure, erroneous readings due to the vis
viva and inertia of the moving parts being eliminated by the controlling
action of the apparatus herein-before described.
Figure 1 of the accompanying Drawings is a face view (with the dial
plate and protecting cage removed); Figure 2, a longitudinal section;
and Figure 3, a transverse section shewing one modification or arrange-
ment of our improved pressure gauges.
a is a metal case with a glass face b, and nearly filled with a trans-
parent and stable liquid, such as glycerine; c is an air chamber com-
municating with the case a by means of a channel or passage d; e is a
cylinder of somewhat smaller capacity than the chamber c, and con-
taining a piston f, the rod g of which bears at its outer end against a
spring h. This spring is covered with an elastic diaphragm i, which is
connected through the aperture or passage with the fluid whose
pressure it is required to indicate. The hole in the cylinder cover 7,
through which the piston rod g is taken is made slightly larger than the
rod; the diameter of the cylinder e is also slightly larger than that of
the piston, and the rod may also work loosely in the outer end of the
cylinder, so that the glycerine may fill all parts of the instrument up to
the spring h. The rod g is connected to the indicating arm m of the
gauge by means of a rack n and pinion o, as before described. A maxi-
mum indicator p is actuated in one direction only by the indicating arm
by means of the projection q, and is set by hand at zero by means of
pinions 1, 1, and a set rod & passing through a stuffing box fixed either
in the back of the case a, as shewn, or in the glass face or in the side of
the case, in which last-named position bevil gearing is necessary. The
set rod is provided with a key or button either movable or fixed to the
rod; is the dial plate, and a protecting cage or skeleton cover; wis
a spiral spring which presses the piston rod 9 against the spring hand
diaphragm i.
The action of the gauge can be readily understood by the explanations
herein-before given.
We prefer that the spring w should be a spiral spring surrounding
the piston rod and formed from an uniform steel wire, as we have found
by experiment that other forms of spring as at present made cannot be
donandod unon to not uniformly The
when nood fom taki

page_text: deep sea soundings will when sunk in the sea by means of a lead to any,
up to a certain depth, and then brought to the surface, record by means
of the maximum indicator p the greatest pressure to which it has been
subjected, and from this record the depth to which the gauge sunk can
be ascertained; or the dial can be graduated so that this depth can be
read off at once.
Figure 4 is a face view, and Figure 5 a transverse section of a gauge
constructed similarly to that shewn in Figures 1, 2, and 3, except that
a second rack n' is employed on the opposite side of the pinion o, so
that in case the instrument may receive a severe shock the two
racks n, n', may act as compensators one to the other, and for this
purpose the second rack n' should be balanced by sufficiently weighting
it. x is a plate on the end of the rack n' to offer resistance to its
movement through the liquid. A similar plate may be fitted to the
rack n.
Figure 6 is a face view, Figure 7 a longitudinal section, and Figure 8
an end view of a gauge where the piston and cylinder arrangement is
dispensed with, and similar results are obtained by fixing a fan y, y, to
the indicating arm m, so as to offer resistance to the movement of the
parts through the liquid in the case a;,, (Figure 6,) are divisions to
form compartments in the case in order to cause the liquid to partake of
any movement given to the body of the gauge; i is the clastic diaphragm
as before, which is in communication with the outer fluid by the
aperture . In other respects this instrument resembles a Bourdon
gauge.
Figure 9 is a face view, Figure 10 a longitudinal section, and
Figure 11 an end view, with the screw cap A removed, of another
arrangement in which a Bourdon tube is used in combination with a
piston and cylinder, as herein-before described. The increasing outer
pressure forces the diaphragm i inwards, and by thus contracting the
internal space and thereby increasing the pressure within the case, the
free end of the scaled tube B acts upon the toothed sector C, and moves
the pinion o of the indicating arm. This movement is controlled and
sudden fluctuations prevented by attaching the sector C to the piston
rod g, the piston f of which fits the cylinder e loosely, but not so loosely
as to allow the fluid to pass too easily. This cylinder and the case being
filled with glycerine, the rapidity of the movement of the sector C is

page_text: limited by the rate at which the glycerine can pass between the piston f
and its cylinder e.
It is part of our Invention, independently of any particular
arrangement for controlling the moving parts of the instrument, to
employ an elastic diaphragm and to fill such portion or portions of the
gauge inside such diaphragm, to which it may be wished to carry the
external fluid pressure with a transparent and stable liquid such as
glycerine. We thus prevent the external fluid entering the gauge and
acting destructively upon the metal parts thereof.
And having now described the nature of our said Invention and in
what manner the same is to be performed, we declare that we claim as
our "Improvements in Gauges for Indicating Fluid Pressures,"-
First. Constructing gauges so that the movements of the parts are
controlled and violent fluctuations of the indicating arm prevented.
substantially by the means and in the manner herein-before described.
Second. Constructing gauges substantially as herein-before described
and represented in the annexed Drawings.
Third. The employment in gauges of an elastic diaphragm and the
filling of the gauge inside such diaphragm with glycerine or other stable
liquid, as and for the purpose herein-before described.
In witness whereof, I, the said Louis Paschal Casella, on behalf
of myself and the said John Townsend Bucknill, have hereunto
set my hand and scal, this Third day of February, One
thousand eight hundred and seventy-six.
LOUIS P. CASELLA. (L.S.)