IMPROVEMENTS IN MERCURIAL GAUGES
Year: 1886

page_text: I, HENRY JAMES HOGG KING of Newmarket near Stroud Gloucestershire
Engineer do hereby declare the nature of my invention for IMPROVEMENTS IN
MERCURIAL GAUGES to be as follows:-
--
This Invention relates to Improvements in Mercurial Gauges one of the objects
of which is to record a high pressure without any long length of glass tube and
at the same time so make it, that the vertical height of the column of mercury
can be measured at any time, and the accuracy of the scale tested by actual
measurement.
When made in this way the gauge is also very convenient for transport is easily
filled and is not liable to break-Further improvements consist in making the tap
automatically close itself when this gauge is used as a vacuum gauge this prevents
its being blown out when the engine starts, or from excess of pressure, this tap
being also applicable to other vacuum gauges-Another improvement consists in
providing a small cistern which is attached to the top of the last tube and is used
to catch the mercury in the event of the gauge being blown out from excess of
pressure and adding a whistle which will be blown by the steam which follows,
the mercury, and thus calls attention to the danger.
To effect these objects, I take a short length of glass tube not usually more than
3 ft. long and seal the bottom end, the top end being in connection with the
pressure to be tested. This tube is filled with mercury to the point where it is
intended to begin the scale and into the centre of this tube a much smaller one,
passes nearly to the bottom and passes up to any height required by the pressure
it is intended to indicate. That portion of the tube which passes down the centre
of the large one I prefer to make of glass also, or non metalic for if made of iron
or steel there is a greater liability of the glass breaking-but above the case which
contains the glass tubes I put a metalic tube (by preference a weldless steel tube)
This is put together in short lengths by means of nuts and ground joints and it is
this arrangement which enables the accuracy of the scale to be checked at any
time, besides giving facility of transport-for as the lengths are attached one by

page_text: one the mercury may be brought, within a short distance of the top of each, and
the height of the column carefully measured-To the last length of tube at the top
a small cistern may be advantageously added to catch the mercury should the
gauge be blown out, and this is so arranged that the mercury falls to the bottom of
the cistern and leaves a clear passage way for the steam following to blow a whistle
and cause an aların. When this gauge is used as a combined vacuum & pressure
gauge, or a vacuum gauge only, I use a tap which automaticaly closes itself and
prevents any sudden rush of steam or pressure blowing it out. This consists of
a valve which shuts down on a seat, and is kept there by a spring or gravity.
A handle is attached to lift this valve by hand when the gauge is used. When
this gauge is used for testing purposes, and is not attached to the boiler I fit
a small pump on the gauge by which the necessary pressure is obtained. .

page_text: Improvements in mercurial Gauges.
I, HENRY JAMES HOGG KING of Newmarket near Stroud, Gloucestershire
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 :-
This Invention relates to Improvements in Mercurial Gauges one of the objects
of which is to record a high pressure without any long length of glass tube and at
the same time so make it, that the vertical height of the column of mercury can
be measured at any time, and the accuracy of the scale tested by actual measure-
ment. When made in this way, the gauge is also very convenient for transport, is
easily filled and is not liable to break. Further improvements consist in making
the tap automatically, close itself, when the mercurial gauge is used as a vacuum
gauge this prevents its being blown out when the engine starts by excess of
pressure in the condensor. Another improvement consists. in providing a small
cistern which is attached to the top of the last tube of the pressure gauge, and is
used to catch the mercury in the event of the gauge being blown out from excess
of pressure, above the cistern (if desired) a whistle can be placed, which would be
blown, by the steam which follows the mercury, and thus sound an alarm, and in
order, that my said Invention may be properly understood, I append hereto a sheet
of explanatory drawings.
Figs. 1 & 2 show front and side elevations, of the pressure gauge and Fig. 3 an
enlarged sectional view of the same. Figs. 4 & 5 show a full size sectional view
& elevation of the vacuum gauge-1 is a glass tube shown in section in Fig. 3, the
lower end of which is hermetically sealed, and the upper end passes through the
stuffing gland 2 the joint being made by the India rubber washers-3. Down
the centre of the glass tube, and nearly reaching the bottom of the same, the sinall
tube 4 passes which we will assume is the area of the glass tube 1. 5 is the
passage which communicates with the boiler or outside pressure to be tested by
the gauge. If the glass tube is now filled with mercury, to the levels shown at 6,
and the pressure is applied, it will drive the mercury down the glass tube and up
the small tube, 20 times the height that the mercury falls in the large one-till
the pressure is balanced, by the column of mercury. The principle feature in this
gauge consists in making the tubes 7 & 8, &c. in comparatively short lengths, and
coupling them together by the nuts 9-By this means the accuracy of the gauge
can be tested at any time, by actual measurement from the 2 surfaces of the
mercury in the small tube and that in the glass tube. To make the gauge sound
an alarm, should the pressure rise so high, as to blow the mercury out-I attach
an ordinary steam whistle 10 to the top tube in connection with a vessel 11 to
catch the mercury as it is blown out, and the steam then rushes through the whistle
and sounds an alarm. Should this gauge be used for testing purposes an extra
tap 12 can be used, and the ordinary gauge to be tested, attached as shown in
Fig. 1. A small hand pump may also be used for pumping up the pressure as
shown by the dotted lines.
1
To prevent oxidation, and any effects from frost-I use glycerine above the
mercury and I varnish the small steel tubes over to prevent their rusting.

page_text: Figs. 4 & 5 show a Mercurial Vacuum Gauge, the principal feature of which
consists in the tap A. which is so made, that it automatically closes itself. The
valve 14 being kept down to its seat by a powerful spiral spring 15, the spindle of
this valve passes up through the gland 17 and ends in the nob, 18, under which
the handle 19 is placed. When the vacuum is wished to be known, it is only
necessary to press down the handle 19, when the valve 14 will be lifted, and the
vacuum shown by the column of mercury in the glass tube. As soon as the
handle 19 is released the valve closes, and prevents any pressure, (which often
occurs in the condensor when the engine starts from blowing out the mercury, this
having previously been the great defect in Mercurial Vacuum Gauges.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed--I declare that what
I claim is:
1st. The use (in a differential mercurial pressure gauge of the same kind as
shown in Figs. 1-2 & 3) of the short lengths of metalic tubes 7-8, &c. which
can be readily coupled together in a similar way to that shown, by which means
the accuracy of the gauge can be tested at various pressures by actual
measurement.
2nd. The use of a Whistle to sound an alarm in connection with a mercurial
pressure gauge when the pressure in the boiler becomes too high.
3rd. The use of a cistern 11 to prevent the mercury being wasted, should the
gauge be blown out by excess of pressure.
4th. The use of Weldless Steel Tubes in a gauge of this description.
5th. The use of Glycerine in the glass tubes and gauge above the mercury to
prevent rust.
6th. The use in a Mercurial Vacuum Gauge, of a tap which shall automatically
shut itself, substantially as shown in Figs. 4 & 5 so that the mercury cannot be
blown out by any pressure in the condenser, which is liable to occur during the
starting of the engine.
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