IMPROVEMENTS IN PRESSURE GAUGES
Year: 1878

page_text: LETTERS PATENT to John Spalding Parfitt, of King's Heath, in the County of
Worcester, Mechanical Engineer, for the Invention of "IMPROVEMENTS IN
PRESSURE GAUGES."
Sealed the 10th May 1878, and dated the 1st March 1878,
PROVISIONAL SPECIFICATION left by the said John Spalding Parfitt at the
Office of the Commissioners of Patents on the 1st March 1878.
JOHN SPALDING PARFITT, of King's Heath, in the County of Worcester,
Mechanical Engineer. IMPROVEMENTS IN PRESSURE GAUGES."
"
My Invention has reference to pressure gauges in which a series of vertical
columns of mercury alternating with columns of some lighter liquid are employed,
the pressure being indicated by the height of the mercury in the tubes.
These gauges are ordinarily made of a long glass tube, bent or folded upon itself
several times so as to form a tube of a zig-zag figure, that is, of the figure of a series
of parallel tubes, connected together at their tops and their bottoms.
In making the said gauges according to my Invention I employ, by preference, a
series of iron or steel tubes, or tubes made of a metal or alloy not injuriously
affected by mercury. One of the tubes, and preferably the last, I make of glass, in
order that the height of the mercury in it may be seen. The length and number
of the tubes is determined by the greater or less pressure which the gauge is
intended to measure. These tubes are connected at top and bottom by means of
metallic connections, which permit of the tubes being connected so as either to
form a continuous zig-zag tube or to communicate with each other at their tops and
at their bottoms.
In preparing the gauge for use the tubes are put into communication at top and
at bottom, and mercury is poured in at the end tube until the tubes are filled to
about half their height. The upper halves of the tubes are then filled with a

page_text: mixture of glycerine and water, or other light liquid not liable to freeze, and with-
out action on mercury or on the metal of which the tubes are made. The com-
munications between the bottoms of the several tubes and the communications
between their tops are closed, and the series of tubes is connected into one con-
tinuous zig-zag tube, the lower halves of the several vertical parts and the lower
bends being filled with mercury, and the upper halves and the top bends being filled
with the mixture of glycerine and water.
When pressure is turned on the tube at one end the compound column of glycerine
and mercury is forced forward until by the lowering of the mercury in alternate
parts of the zig-zag tube and its corresponding rise in the intermediate parts a state
of equilibrium is produced. The excess of the pressure of the longer columns of
mercury over the shorter columns, diminished by the excess of the pressure of the
longer columns of glycerine and water over the shorter columns, constitutes the
amount of resistance presented to the steam or the fluid whose pressure is to be
measured, and the compound liquid column comes to rest when the pressure of the
steam and the resistance of the compound column are equal. The pressure to be
measured is indicated on a graduated scale attached to the last (or other) tube.
To prevent injury to the gauge by sudden pressure a safety valve may be placed
on the end of the last tube.
Although I prefer to make the tubes and the connections at top and bottom of
iron or steel, yet the said tubes may be made of glass or porcelain.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by the
said John Spalding Parfitt in the Great Seal Patent Office on the 16th August
1878.
JOHN SPALDING PARFITT, of King's Heath, in the County of Worcester,
Mechanical Engineer. "IMPROVEMENTS IN PRESSURE GAUGES."
My Invention has reference to pressure gauges in which a series of vertical
columns of mercury alternating with columns of some lighter liquid are employed,
the pressure being indicated by the height of the mercury in the tubes.
These gauges are ordinarily made of a long glass tube, bent or folded upon itself
several times so as to form a tube of a zig-zag figure, that is, of the figure of a series
of parallel tubes, connected together at their tops and bottoms.
Figure 1 of the accompanying Drawing_represents in elevation a pressure gauge
made according to my Invention; and Figure represents the same, partly in
section, and with the casing and graduated scale removed.
Figures 3, 4, 5, 6, 7, 9, and 10 represent parts of the guage, as herein-after
explained; and Figure 8 represents a cross section of the complete gauge taken
through the line D, D, Figure 1. The said Figures 3, 4, 5, 6, 7, 8, 9, and 10 are
drawn to a scale double that of Figures 1 and 2.
The same letters of reference indicate the same parts in the several Figures of
the Drawing.
In making the said guages according to my Invention I employ, by preference, a
series of iron or steel tubes, or tubes made of a metal or alloy not injuriously affected
by mercury. These tubes are marked a in the Drawing. One of the tubes, and
preferably the last, I make of glass, in order that the height of the mercury in it
may be seen.
The length and number of the tubes is determined by the greater or
less pressure which the gauge is intended to measure. These tubes are connected
at top and bottom by means of metallic connections, which permit of the .tubes
being connected so as either to form a continuous tube or to communicate with
each other at their tops and at their bottoms.
The connections of the tubes at top and bottom are arranged as follows:-The
ends of the tubes after passing through the plates a³, one of which is shown
separately in Figure 9, are fixed in the plates b, b; the upper plate b is represented
separately in Figure 3. Upon these plates b, b, are other plates c, c, having in them
a series of tangential grooves d, d, as represented in the separate Figures of the
said plates. Figures 4 and 5, Figure 4 representing the bottom plate c, and Figure 5
the top plate c. The top plate c differs from the bottom plate c in having the radial
groove e by which the steam or other pressure is transmitted from the central pipe t
to the beginning of the zig-zag tube.
Figures 6 and 7 represent respectively sections of the plates c,. c, Figures 5 and 4,
and the appliances connected therewith for effecting the requisite changes in the
top and bottom connections of the tubes. The section, Figure 6, is taken on the
line a, a, Figure 5; and the section, Figure 7, is taken on the line b, b, Figure 4.
I will first describe the arrangement at the top of the tubes. In each of the
tangential grooves d, Figure 5, is a vertical passage f (see Figure 6) opening into
the circular groove g. When the passages fare open all the tubes cominunicate at
top with each other through the circular groove g, but when the passages fare
closed the tubes communicate at top with each other through the tangential
grooves d, and the top of each tube of the inner series communicates with the top
of one of the tubes of the outer series, as will be understood by an examination of
Figure 5. This closing of the passages f is effected by the tubular collar h. An
india-rubber ring i, placed in the circular groove g, is pressed by the descent of the
collar h upon the tops of all the passages f, and the said passages are thereby closed,
the several tubes now only communicating by the tangential grooves d. The raising
and lowering of the collar h is effected by the screw and nuts k, Figures 1 and 2.

page_text: I will now describe the arrangement at the bottoms of the tubes. This arrange-
ment is essentially the same as that at the top, excepting that the parts are inverted,
and the india-rubber ring or plate is arranged differently, so that the groove g may
retain the mercury whether the passages f are opened or closed. The bottom plate c
Figures 4 and 7, contains the same tangential passages d as the top plate c, Figures 5
and 6, but has not the radial groove e. It has also the circular groove g into which
the passages fopen. The closing of the said passages f, Figures 4 and 7, is effected
differently. q is a broad ring of india-rubber covering the circular groove g; a
series of pegs 1, 1, is carried by the collar m. These pegs pass through guide holes
in the pressing plate n, the rounded tops of the pegs 1, 1, being respectively under
the bottoms of the passages f. When by the screw and screw nut at p, Figure 2,
the collar m is raised each of the passages fis closed by the rounded top of one of
the pegs pressing the india-rubber ring q tightly against the bottom of the said
1
passages f
In preparing the gauge for use the tubes a are put into communication at top
and at bottom by relaxing the screw nuts kand p, and mercury is poured in at the
top circular groove g, Figure 6, passing through the passages f until the tubes are
filled to about half their height. The upper halves of the tubes are then filled with
a mixture of glycerine and water, or other light liquid not liable to freeze, and
without action on mercury or on the metal of which the tubes are made. The com-
munications between the bottoms of the several tubes and the communications
between their tops are closed by means of the screws and nuts at k and p, and the
series of tubes is converted into one continuous zig-zag tube, the lower halves of
the several vertical parts and the lower bends being filled with mercury, and the
upper halves and the top bends being filled with the mixture of glycerine and
water.
When pressure is turned on the tube at one end through the central passage t the
compound column of glycerine and mercury is forced forward until by the lowering
of the mercury in alternate parts of the zig-zag tube and its corresponding rise in
the intermediate parts a state of equilibrium is produced. The excess of the pressure
of the longer columns of mercury over the shorter columns, diminished by the excess
of the pressure of the longer columns of glycerine and water over the shorter
columns, constitutes the amount of resistance prosented to the steam or the fluid the
pressure of which is to be measured, and the compound liquid column comes to rest
when the pressure of the steam and the resistance of the compound column are
equal. The pressure to be measured is indicated on a graduated scale s attached
to the case, as in Figures 1 and 8.
Figure 10 represents a safety valve (marked u in Figure 1), which prevents the
mercury from being forced out of the tubes by too great an increase of pressure.
It consists of a small cup fitted to the end of the last tube of the gauge, in which
cup is a float carrying a valve. If the pressure in the gauge is too much increased
the mercury in the last tube will rise into the cup and lift the float, thereby closing
the valve and preventing the mercury from overflowing.
Although I prefer to make the tubes and the connections at top and bottom of
iron or steel yet the said tubes and connections may be made of glass, or porcelain,
or other materials, such as gutta percha or india-rubber,
By constructing the said gauges according to my Invention their manufacture is
simplified, their adjustment is readily effected, and in case of injury one or more of
the tubes may be readily removed and replaced.
Having now described the nature of my Invention, and the manner in which the
same is to be performed, I wish it to be understood that I claim as my Invention of
improvements in pressure gauges of the kind described,―
The construction and arrangement of parts, substantially as described and
illustrated in the accompanying Drawing, for connecting the tops and the bottoms
of the series of tubes constituting the gauge, so as to convert the tubes of the series
at pleasure either into one continuous zig-zag tube, or to put the tops of all the
tubes into communication with each other, and also all the bottoms of the tubes

page_text: into communication with each other, whereby the construction, filling adjustment,
and repair of the gauge are much facilitated.
Also the valve, Figure 10, for preventing the overflow of the mercury in gauges
constructed according to my Invention, and in gauges of like construction.
In witness whereof, I, the said John Spalding Parfitt, have hereunto set my
hand and seal, this Thirteenth day of August, in the year of our Lord One
thousand eight hundred and seventy-eight.