Improvements relating to Pressure-gauges.
Year: 1891

page_text: Improvements relating to Pressure-gauges.
We, JOHN JACKSON Engineer, and EDWIN ALFRED HOAD, Manufacturer both
of Suffolk House, Lawrence Pountney Hill, in the City of London, 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 relates to pressure-gauges and is designed to provide for permitting
the escape of gas or other fluid from the interior of the gauge when from any cause
the pressure of such gas or other fluid rises to or beyond the limit which the
gauge is constructed, or when any other predetermined pressure is attained or
exceeded.
The chief object of our said invention is to afford increased safety in the use of
pressure-gauges on bottles or other vessels charged with gases (more especially
oxygen gas) under very high pressure. Explosions have in some instances occurred
from chemical combustion and other causes in the interior of pressure-gauges so
employed, and there is consequently considerable danger in the use for this purpose
of pressure-gauges as heretofore constructed.
Now according to our present invention we construct the pressure-gauge with a
suitable safety device whereby any undue or excessive pressure will be relieved
by permitting the escape of the gas or other fluid from the interior of the gauge.
We thus obviate the liability to bursting of the gange should an explosion occur
therein, or in the bottle or other vessel to which it is connected. Our said invention
is also applicable with advantage to pressure-gauges intended to be used with
more moderate pressures, for instance, to pressure-gauges to be employed on steam-
boilers and the like.
In the accompanying drawing, we have shown how our said invention may be
conveniently and advantageously carried into practice.
Figure 1 is a side elevation, partly in vertical central section, showing one form
of our improved pressure-gauge constructed with a safety or relief valve which
communicates directly with the fluid-passage or inlet of the gauge.
Figure 2 is a side elevation, a portion of the outer casing being removed, showing
another form or modification of our improved gauge wherein a safety or relief valve
is provided upon the bent or "Bourdon" tube of the gauge.
Figure 3 is a side elevation, partly in vertical section, showing a further modifi-
cation of our invention, and
Figures 4 and 5 are sectional elevations showing still further modifications of our..
said invention.
Like letters indicate corresponding parts in these figures.
a is the outer casing of the gauge; b is the screw-threaded stem or inlet pipe ;
e is the bent or Bourdon tube of the gauge.
The safety or relief valve for preventing over pressure in the gauge, comprises
a valve-chamber d attached to the stem b, or to the part d' of the tube c, as the case
may be. This valve-chamber d is screw-threaded externally as shown, and is
provided at its inner end with a valve-seat d. It communicates by a passage d
either with the fluid-passage or inlet of the gauge as shown in Figure 1, or with
the interior of the Bourdon" tube c, Figure 2. A valve provided with a
stem is arranged within the chamber d and is fitted to the seat d'. The said
valve is held against its seat by a spiral spring f surrounding the valve-stem e¹ and

page_text: enclosed in a chamber d. A cap or cover is screwed upon the valve-chamber d
and is provided with a central aperture through which projects the extremity of the
valve-stem e¹.
The outer end of the spring bears against this cap or cover g, so that, by scerwing
the said cap or cover further upon the chamber d or unscrewing it therefrom, the
pressure which the spring exerts upon the valve e can be regulated as required.
A lock-nut is provided upon the valve-chamber d to retain the cap or cover 9 in
any position to which it may be adjusted. Or in place of using a lock-nut, we can
secure the cap or cover by a pin to prevent any alteration in its adjustment. Or it
may be otherwise constructed and arranged for this purpose.
The chamber d is, morcover, provided with one or more apertures or vents (³
for the escape of any gas or other fluid that may pass through the safety-
valve.
In the apparatus shown in Figure 2, wherein the safety-valve is secured upon the
extremity of the "Bourdon" tube c, and consequently moves with the same, I
provide a slot or opening in the rear of the casing a, in which the said safety-valve
may move to and fro or up and down; and I provide over the said opening a
casing or cover for the purpose of protecting the valve. In the modification
illustrated in Figure 3, the vents or apertures for the escape of the gas or other fluid
from the chamber or casing d have fitted therein tubes which extend through
holes in the casing or cover j.
The arrangement of the safety-valve on the "Bourdon" tube, as shown in
Figure 2 or Figure 3, is advantageous in testing the gauge by hydraulic pressure,
as the air can be forced out through the said safety-valve, the liquid being introduced
into the gauge until all the air is expelled therefrom and liquid begins to flow
through the said valve.
In using a pressure-gauge provided with my present improvements, the cap or
cover should be so adjusted that, when the pressure in the gauge rises above the
limit for which the gauge is constructed, or any other predetermined limit, the
spring will be compressed and the safety-valve opened to allow the escape of the gas
or other fluid from the interior of the gauge.
It is obvious that we can, if desired, employ any other convenient form of safety-
valve in place of that above described, and that the said valve may be secured to
any other suitable part of the gauge for the purpose above specified.
Moreover instead of the said valve being retained upon its seat by a spring, it
may, if desired, be held thereon by a screw-threaded plug k, Figure 4, fitted in a
suitable fixed internally screw-threaded portion or mut 7, the screw-threads being
made so weak, or so few threads being used as to ensure stripping of the same when
any undue pressure acts upon the valve. Or instead of employing a valve, we may
employ a suitable plug or stopper m, Figure 5, fitted and secured in such a manner
as to close the end of the passage d² or any other suitable aperture or passage, and
adapted to be forced out when the pressure in the gauge rises to or beyond that for
which it is constructed.
It is evident that our improvements are applicable to other kinds of gauges, for
instance to diaphragm-gauges.
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 is :-
First. A pressure-gauge provided with suitable means for permitting the escape
of the gas.or other fluid therefrom when any predetermined pressure is attained or
exceeded therein.
Second. A pressure-gauge wherein a safety-device for the purpose above specified
is fitted upon the bent or Bourdon" tube thereof.
Third. A pressure-gauge provided with a safety-valve constructed and arranged

page_text: substantially as described with reference to Figure 1 or to Figure 2 of the accom-
panying drawings and operating as, and for the purpose, above specified.
Dated this 22nd day of January 1891.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicants.