Improvements in Pressure Gauges.
Year: 1896

page_text: PROVISIONAL SPECIFICATION.
Improvements in Pressure Gauges.
I, FREDERICK EDWARDS, of 62 Bishopsgate Street, Within, London E.C., Consulting
Engineer, do hereby declare the nature of this invention to be as follows:-
My invention relates to improvements in the construction of pressure gauges
and more particularly to low pressure gauges. In low pressure mercurial gauges
as heretofore usually constructed for use in connection with condensers, the height
of the mercury in the reservoir or enlarged shorter arm of the bent tube is
generally out of sight, or if it be in sight, there is nothing to show that the
mercury in it is standing at the proper level.
Now my invention has reference to a construction of mercurial pressure gauge
in which the reservoir is completely in sight, and scales are provided in proximity
to such reservoir and to the long arm of the tube whereby the level of the mercury
can be readily seen and the pressure within the space with which the open end of
the reservoir communicates can be read off in suitable units, such as inches and
pounds pressure per square inch, on both the long tube and the reservoir, that is
to say both the height of the mercury and the corresponding pressure can be read
off in two places at the same time, and, if the gauge is recording the pressure
correctly, the two readings will be the same. This arrangement therefore affords
a means of checking the accuracy of the gauge and with this object a notice is
placed below the scales to the effect that if the two readings agree, the gauge is
correct.
The gauge is constructed as hereinafter explained, so that any person using it
can easily take out the scales, check them with a rule and measure how much has
been allowed by the maker of the instrument for the vapour of mercury present in
the tube. The gauge is also constructed with a scale of temperatures, that is to
say, a scale indicating the temperature due to each pound pressure of steam per
square inch, and tenth of a pound per square inch so that the proper temperature
due to any indicated pressure within the range of the instrument can instantly
be seen.
The gauge comprises a plain glass tube the upper and lower ends of which take
into grooves formed in top and bottom plates and are caused to bear tightly against
india rubber packing rings in said grooves, so as to form an air tight joint therewith,
by drawing the plates together by means of bolts. In this way an air tight joint can
be easily made without the use of shellac or other inconvenient material; so that
spare glass tubes can be carried and easily put in position to replace a broken one,
and the scales hereinafter referred to can easily be taken out for any desired purpose,
all joints being capable of being easily broken and reliably renewed; the instrument
is thus rendered more durable than heretofore. Within the tube is a vertical plate or
support carrying the mercurial gauge tube consisting of a long arm and a short arm
or reservoir. On the plate at opposite sides of the long arm are two scales one to
indicate the heights of mercury in inches and tenths of an inch, and the other to
indicate the corresponding pressures in pounds and tenths of a pound per square inch.
Corresponding scales are arranged at opposite sides of the shorter arm or reservoir
these scales being arranged to overlap the lower ends of the scales at opposite sides
of the long arm by an amount sufficient to compensate for the presence of vapour
of mercury in the long arm of the gauge tube so that at zero pressure, the level of

page_text: the mercury in each arm shall be exactly opposite the zero mark on each scale.
A scale of temperatures is arranged on the vertical plate adjacent to the scale of
pressures opposite, the long arm of the gauge tube and its indications represent
the temperatures corresponding to the several condenser pressures represented in the
said pressure scale and therefore the temperature below which the feed water should
not leave the condenser at the various pressures indicated to obtain maximum
economy. The vertical plate is fixed at the top to a bolt that extends through the top
plate and has screwed on its outwardly extending end a ring or bandle by which
the gauge can be suspended from any suitable support. Packing rings are provided
to effect an air tight closure between the bolt and the top plate. The arrangement
is such that by slightly unscrewing the ring or handle and applying a spanner to
a squared part of the bolt the vertical plate with the gauge tube and scales carried
thereby can be turned partly round (without opening the instrument) to the most
convenient position for the light to fall upon it and admit of the easy reading of
the scales, after which the ring or handle is again tightly screwed up. The lower
end of the plate is steadied by a pin that is flattened at opposite sides and fits into
a hole in the bottom plate by which the interior of the closed tube is placed in
communication with two lower branches. These branches are adapted to be
connected the one with a condenser and the other with an engine cylinder or other
vessel the degree of pressure in which it is desired to ascertain. These branches are
provided with cocks by which either connection can be closed or opened at will. One
of the connections is to be permanently connected to the condenser in the usual way,
the other being fitted with a union, flexible suction pipe, valve and gear for connecting
the gauge without moving it to the L.P. cylinder in order that the lowest pressure,
or the lowest pressure at any particular part of the stroke in the top and bottom
ends of the cylinder, may be easily and quickly seen, compared with the pressure
in the condenser, and the difference in the pressures and the loss at various powers
and speeds accurately ascertained. The valve may be constructed and arranged in
various ways so that it will open at certain portions of the stroke of the piston
in the said cylinder. In one arrangement the valve proper is an automatic suction
flap valve and comprises a piece of flexible sheet material such as leather fixed at
one edge and faced on opposite sides with metal plates one of which is adapted to
bear upon a suitably arranged seat. The valve case is pivoted by trunnions in a
fork in which it can be fixed in any desired position by a set screw. The special
features of this arrangement are that the valve can be made of such a weight as
may be most suitable for different purposes, and the valve-box being hung by
trunnions can be placed in such positions or at such angles that the weight of the
valve proper nearly approaches, is equal to, or is more than the power required to
make the valve leave its seat, so that it will overcome the adhesive properties of
grease or other substance that may be on the valve and which tends to prevent
the valve opening by suction.
In another arrangement the valve is opened and closed mechanically. The valve
in this case is carried by a rod and is arranged to be opened by a vertically movable
rod driven from the engine to be tested, or from the indicator gear thereof and
acting by means of a tappet on a spring pawl carried by the outer guided end of
the valve rod. The pawl is mounted to turn upward when the tappet engages its
underside, but on the downward movement of the tappet is pressed outward so as
to open the valve against the action of a spring which closes it immediately the
tappet passes below the pawl. When this arrangement of valve is used the gauge
will indicate the pressure at that particular part of the stroke at which the valve
is arranged to open. Thus it becoines possible to easily, quickly, and accurately see
the pressure in the condenser, in the cylinder, in the air pump or other device to
which the gauge is connected, at various parts of the stroke of an engine and at
various powers and speeds thereof, and also to ascertain the difference between the
pressure in the L.P. cylinder at the time of the exhaust and that in the condenser.
The gauge is constructed with a strong outer case consisting of two cylindrical
"portions so arranged that when both are pushed down, the whole of the internal
L

page_text: delicate parts are well protected. The upper portion can be raised just as much as
may be required in ordinary use, the lower parts of the gauge remaining protected;
or if it be desired to check the readings, both portions of the case may be raised.
Thus by first raising the upper portion, the whole of the upper internal parts of the
gauge can be seen and then by raising the lower portion the whole of the lower
internal parts can be seen. On the outside of the case are placed such instructions as
may be of service to users of the gauge.
The outer case and the bolts for holding the top and bottom plates and glass tube
together and on which lugs on the interior of the case can slide, are so constructed
and arranged that the said case cannot be put on wrongly, that is to say so that the
instructions or other information on the case will be at the back of the instrument and
therefore out of sight when the instrument is in position for use. For this purpose
two of the bolts may be at a greater distance apart than the other two.
FRED. EDWARDS.
I, FREDERICK EDWARDS, of 62 Bishopsgate Street Within, London, E.C.,
Consulting 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 :-
My invention relates to improvements in the construction of pressure gauges and
more particularly to low pressure gauges. In low pressure mercurial gauges as
heretofore usually constructed for use in connection with condensers, the height of
the mercury in the reservoir or enlarged shorter arm of the bent tube is generally out
of sight, or if it be in sight, there is nothing to show that the mercury in it is standing
at the proper level.
Now my invention has reference to a construction of mercurial pressure gauge in
which the reservoir is completely in sight, and scales are provided in proximity to
such reservoir and to the long arm of the tube whereby the level of the mercury can
be readily seen and the pressure within the space with which the open end of the
reservoir communicates can be read off in suitable units, such as inches and pounds
pressure per square inch, on both the long tube and the reservoir, that is to say both
the height of the mercury and the corresponding pressure can be read off in two places
at the same time and, if the gauge is recording the pressure correctly, the two readings
will be the same. This arrangement therefore affords a means of checking the
accuracy of the gauge and with this object a notice is placed below the scales to the
effect that if the two readings agree, the gauge is correct.
The gauge is constructed as hereinafter explained, so that any person using it can
easily take out the scales, check them with a rule and measure how much has been
allowed by the maker of the instrument for the vapour of mercury present in the tube.
The gauge is also constructed with a scale of temperatures, that is to say, a scale
indicating the temperature due to each pound pressure of steam per square inch, and
tenth of a pound per square inch so that the proper temperature due to any indicated
pressure within the range of the instrument can instantly be seen.
In the accompanying drawings,
Fig. 1 is a vertical section, partly in elevation, showing the upper portion of a
low pressure gauge constructed according to this invention, and Fig. 1 is a front
elevation of the lower portions thereof.
Figs. 2 and 2 are elevations of the upper and lower portions as seen in a
direction at right angles to Figs. 1 and 1ª.
Fig. 3 is a horizontal section on the line of Fig. 1.

page_text: The gauge comprises a plain glass tube 1 the upper and lower ends of which take
into grooves 2, 2 formed in top and bottom plates 3 and 3 respectively and are
caused to bear tightly against india rubber packing rings 4, 4ª in said grooves, so as
to form an air tight joint therewith, by drawing the plates together by means of
bolts 5. In this way an air tight joint can be easily made without the use of shellac
or other inconvenient material; so that spare glass tubes like 1 can be carried and
easily put in position to replace a broken one, and the scales hereinafter referred to
can easily be taken out for any desired purpose, all joints being capable of being easily
broken and reliably renewed; the instrument is thus rendered more durable than
beretofore. Within the tube 1 is a vertical plate or support 6 carrying the mercurial
gauge tube consisting of the long arm 6 and the short arm or reservoir 6°. On the
plate at opposite sides of the long arm 6 are scales 7 and 8 of which 7 serves to
indicate the heights of mercury in inches and tenths of an inch, and 8 to indicate the
corresponding pressures in pounds and tenths of a pound per square inch. 7 and 8
are corresponding scales arranged at opposite sides of the shorter arm or reservoir 6,
they are arranged to overlap the lower ends of the scales 7 and 8 by an amount
sufficient to compensate for the presence of vapour of mercury in the long arm of the
gauge tube so that at zero pressure, the level of the mercury in each arm shall be
exactly opposite the zero mark on each scale. 9 is a scale arranged on the plate 6*
adjacent to the scale of pressures 8 and the indications of which represent the
temperatures corresponding to the several condenser pressures represented in the
pressure scale 8 and therefore the temperature below which the feed water should not
leave the condenser at the various pressures indicated to obtain maximum economy.
The plate 6 is fixed at the top by a bolt 10 to an eye bolt 11 that extends through
the top plate 3 and has screwed on its outwardly extending end a ring or handle 12
by which the gauge can be suspended from any suitable support. 13, 13" are packing
rings to effect an air tight closure between the eye bolt and the top plate 3. As will
be seen the arrangement is such that by slightly unscrewing the ring or handle 12
and applying a spanner to the squared end 11 of the eye bolt 11 the plate 6 with the
gauge tube and seales carried thereby can be turned partly round (without opening
the instrument) to the most convenient position for the light to fall upon it and admit
of the easy reading of the scales, alter which the ring or handle is again tightly
screwed up. The lower end of the plate 6 is steadied by a pin 13 that is flatted at
opposite sides and fits into a hole 14 in the bottom plate 3 by which the interior of
the closed tube 1 is placed in communication with lower branches 15 and 16. These
branches are adapted to be connected the one with a condenser and the other with an
engine cylinder or other vessel the degree of pressure in which it is desired to
ascertain. These branches 15 and 16 are provided with cocks 15 and 16" respectively
by which either connection can be closed or opened at will. The gauge is constructed
with a strong outer case consisting of two cylindrical portions 17, 17ª so arranged that
when both are pushed down as shown, the whole of the internal delicate parts are
well protected. The upper portion 17 can be raised just as much as may be required
in ordinary use, the lower parts of the gauge remaining protected; or if it be desired
to check the readings, both portions 17, 17" of the case may be raised. Thus by first
raising the upper portion 17 the whole of the upper internal parts of the gauge can be
seen and then by raising the lower portion 17 the whole of the lower internal parts
can be seen. On the outside of the case 17, 17" are placed such instructions as may
be of service to users of the gauge.
The outer case and the bolts 5 on which lugs on the interior of the case slide are so
constructed and arranged that the said case cannot be put on wrongly, that is to say
so that the instructions or other information on the case will be at the back of the
instrument and therefore out of sight when the instrument is in position for use.
For this purpose two of the bolts 5 may be at a greater distance apart than the other
two. The utility of my improved gauge will be best understood from the following
description.
Supposing it is desired to know what the temperature of the steam is at any given
pressure and whether it contams any superheat, the reading obtained from an ordinary

page_text: kind of pressure gauge subject to the action of the steam has to be added to the
pressure indicated by the barometer at the place where the reading is made and the
temperature due to the total or absolute pressure ascertained from a table. In my
gauge on the contrary the construction is such that the pressure and temperature of
the steam can be seen at once without reference to any other instrument or table.
Again, supposing it is desired to know what the temperature of the feed-water
should be with any particular steam pressure in the condenser. With the ordinary
vacuum gauge (which is generally speaking incorrect) it is necessary to subtract the
reading given thereby from the pressure indicated by the barometer, which instrument
on board ship is generally placed at a higher altitude, as for instance in the chart
room, so that the reading given thereby requires correction, before subtracting from it
the vacuum gauge reading. The temperature corresponding to the absolute pressure
thus obtained from these two instruments has then to be found from a table in which
the temperature due to such pressure is given. In my gauge no reference whatever
has to be made to the two instruments and table and the desired temperature can be
seen if required without reference to the pressure at all.
Some of the advantages of being able readily to ascertain what the temperature
should be, or what the pressure should be under different circumstances, will be best
understood from the following description. Suppose for instance the pressure in the
condenser is far in excess of that due to the temperature of the feed, then the higher
pressure is in all probability due to one large or several small leakages of air which
should be stopped as the efficiency of the condenser, and consequently that of the
engines, is being reduced thereby without any corresponding advantage. Or the
temperature of the feed may have been uselessly lowered by the feed coming in contact
with some cold substance such as circulating water without any corresponding
advantage.
To emphasize the importance of this loss there is or may be provided on the
plate 6 of the gauge a notice stating that "when the temperature of the feed leaving
air pump is less than shown in column due to pressure in condenser there is a loss."
The difference in pressure between that in the condenser and that in the cylinder
exhausting into the condenser is practically speaking all loss and is therefore an
important matter. To ascertain the amount of this loss it is at present necessary to
use the indicator and also the vacuum gauge, and, when the difference between the
two pressures has been ascertained by these two unreliable instruments, neither of the
pressures have been arrived at nor can they be unless a barometer be used. The result
is that to arrive at this loss accurately by the means heretofore employed, is, if at all
practicable, very tedious. The pressure scales 8 8 of my gauge being divided to the
tenth part of an inch, it is quite easy to read the pressure accurately to the twentieth
part of a pound, or even if required to the fortieth part of a pound; this being so it
becomes an easy matter to see exactly what the pressure is in the condenser and in
the cylinder of an engine or other vessel without reference to vacuum gauges or
barometers. My gauge being fitted, as herein before stated, with two branch
pipes 15 and 16 with cocks 15° and 16, it is easy to connect it up with the con-
denser and the low pressure cylinder of an engine by means of flexible, portable, or
fixed pipes, the gauge being then fixed or slung up in any convenient position. In
the connection between the gauge and the low pressure cylinder there is inserted a
valve which may be constructed and arranged in various ways so that it will open at
certain portions of the stroke of the piston in the said cylinder. Fig. 4 is a central
vertical section, Fig. 5 a plan, and Fig. 6 a side elevation at right angles to Fig. 4,
showing one construction of valve for this purpose. The valve proper is a flap valve
and comprises a piece 17 of flexible sheet material such as leather fixed at 18 and
faced on opposite sides with metal plates 19, 19" one of which is adapted to bear upon
a seat at 20. The valve case 21 is pivoted by trunnions 22 in a fork 23 in which it
can be fixed in any desired position by a set screw 24. The special features of this
arrangement are that the valve can be made of such a weight as may be most suitable
for different purposes, and the valve-box being hung by trunnions can be placed in
such positions or at such angles that the weight of the valve proper nearly approaches,

page_text: is equal to, or is more than the power required to make the valve leave its seat, so
that it will overcome the adhesive properties of grease or other substance that may be
on the valve and which tends to prevent the valve opening by suction. When this
arrangement of valve is used the lowest pressure in the connected cylinder during a
stroke will be recorded by the gauge, provided the pressure in the gauge be first
raised above that in the cylinder by admitting air to the tube 1 through a cock 25
(Fig. 14).
Figs. 7 and 8 are elevations at right angles to one another and Fig. 9 a horizontal
section, showing an arrangement for mechanically opening and closing the valve
which controls the communication between the gauge and cylinder. The valve 26 in
this case is carried by a rod 27 and is arranged to be opened by a vertically movable
rod 28 driven from the engine to be tested, or from the indicator gear thereof and
acting by means of a tappet 29 on a spring pawl 30 carried by the outer guided end
of the valve rod 27. The pawl is mounted to turn upward, as indicated by dotted lines
in Fig. 7, when the tappet engages its underside, but on the downward movement of
the tappet is pressed outward so as to open the valve 26 against the action of a
spring 31 which closes it immediately the tappet passes below the pawl. When this
arrangement of valve is used the gauge will indicate the pressure at that particular
part of the stroke at which the valve 26 is arranged to open. Thus it becomes possible
to easily, quickly, and accurately see the pressure in the condenser, in the cylinder, in
the air pump or other device to which the gauge is connected, at various parts of the
stroke of an engine and at various powers and speeds thereof, and also to ascertain the
difference between the pressure in the L.P. cylinder at the time of the exhaust and
that in the condenser.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is:-
1. A pressure gauge of the kind herein referred to comprising scales arranged in
relation to one another and to the respective limbs of the gauge substantially in the
manner described so that the height of the mercury in each limb and the corresponding
pressure can be directly read of by the corresponding scale and the scales opposite
one limb can be used to check the indications of the scales opposite the other limb as
hereinabove explained.
2. A pressure gauge of the kind herein referred to constructed with a scale of
temperatures arranged in proximity to the scale of pressures opposite the mercury
gauge tube and indicating the temperature of steam at different pressures per unit of
area and, fractions thereof, substantially as herein described for the purposes specified.
3. My improved pressure gauge constructed and arranged substantially as berein-
before described with reference to and shown in Figs. 1 to 3 inclusive, with or without
the connecting and controlling means shown in Figs. 4 to 6 inclusive, or in Figs. 7 to 9
inclusive, of the drawings annexed for the purposes specified.
Dated this 2nd day of February 1897.