IMPROVEMENTS IN LOW-WATER ALARM APPARATUS FOR STEAM BOILERS
Year: 1884

page_text: I JOHN HENRY DEWHIRST of 169 Grimesthorpe Road Sheffield in the county
of York Engineer do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN LOW-WATER ALARM APPARATUS FOR STEAM BOILERS" to be as
follows:-
This Invention consists in the construction of a low-water alarm apparatus with
two tubes of different metals, one of which is a better conductor of heat, and
expands more readily, than the other under the influence of equal heat. The most
expansive tube may be plain or corrugated and may be of copper or equivalent
metal or metallic alloy, and this is placed inside the least expansive tube. The
outer tube may be of wrought iron or equivalent metal or metallic alloy. The tubes
are fixed into a bottom frame which is attached to the boiler, so that the water or
steam in the boiler will enter the inner tube. To the top of the outer tube is fixed
a whistle and seat the lower part of the whistle forming the seat of the valve, the
said valve having a stem and head, or piston working in the bell of the whistle the
said valve being retained in its normal position on the valve seat by a spring
acting on the head or piston of the valve stem.
The apparatus is fixed on the side of the boiler at a sufficient depth below
the ordinary water level-called the low-water level-below which it would be
dangerous to allow the level of the water to descend, or if fixed on the top of the
boiler it will be fitted with a tube of a length to reach to the low-water level.
When the water in the boiler is at the working level, or above the opening into the
apparatus water enters and stands in the internal tube, but when the water is
below the opening into the alarm apparatus the tube is emptied of water and its
place is taken by steam which raises the temperature of the inner tube and
expands it and forces up the valve of the whistle, and the whistle is sounded and
continues to sound as long as there is steam in the boiler and water is at or below
the low-water level.
The whistle valve can be fixed to the end of the inner tube or to a cap thereon,
or it may be loose and acted upon by the end of the inner tube.

page_text: I JOHN HENRY DEWHURST of 169 Grimesthorpe Road, Sheffield in the County
of York, Engineer, do hereby declare the nature of my Invention for "IMPROVE-
MENTS IN LOW-WATER ALARM APPARATUS FOR STEAM BOILERS," and in what
manner the same is to be perforined, to be particularly described and ascertained
in and by the following statement :-
This invention consists in the construction of a low-water alarm apparatus with
two tubes of different metals, one of which is a better conductor of heat and
expands more readily than the other under the influence of equal heat. The most
expansive tube may be plain or corrugated and may be of copper or equivalent
metal or metallic alloy, and this is placed inside the least expansive tube. The
outer tube may be of wrought iron or equivalent metal or metallic alloy. The tubes
are fixed into a bottom frame which is attached to the boiler, so that the water or
steam in the boiler will enter the inner tube. To the top of the outer tube is fixed
a whistle and seat, the lower part of the whistle forming the seat of the valve, the
said valve having a stem and head or piston working in the bell of the whistle, the
said valve being retained in its normal position on the valve seat by a spring acting
on the head or piston of the valve stem.
The apparatus is fixed on the side of the boiler at a sufficient depth below the
ordinary working level of the water, called the low-water level, below which it
would be dangerous to allow the level of the water to descend, or if fixed on the
top of the boiler it will be fitted with a tube of a length to reach to the low-water
level. When the water in the boiler is at the working level or above the opening
into the apparatus, water enters and stands in the internal tube, but when the
water is below the opening into the alarm apparatus, the tube is emptied of water
and its place is taken by steam, which raises the temperature of the inner tube and
expands it and forces up the valve of the whistle, and the whistle is sounded, and
continues to sound as long as there is steam in the boiler and water is at or below
the low-water level. The whistle valve can be fixed.to the end of tlie inner tube
or to a cap thereon, or it may be loose and acted upon by the end of the inner
tube.
In order that my invention may be more readily understood and carried into
operation, I will proceed to describe the annexed sheet of drawings.
Fig. 1 is a side elevation of my improved low-water alarm applied to the front
of a boiler; Fig. 2 is a side elevation when applied to the top of a boiler, and
provided with a pipe inside the boiler descending to low-water level; Fig. 3 is
a sectional elevation of one modification of my improved alarm attached to the top
of a boiler. In the cap A, which is fixed to the boiler, is secured the wrought iron
or other equally metallic tube B, on the top end of which is fixed the whistle seat C.
Inside the outer tube B is placed the tube D, made of copper or other equally
expansive metals, the bottom end being secured and fixed into the cap A. The top
end of the tube D extends upwards into the whistle seat C, the top end being just
clear of the valve E. To the valve E is attached the stem F on the upper end of
which is attached the head or piston G working in the bell of the whistle H;
the valve E being retained in its norinal position on its seat by the spring I acting
on the head or piston G, the pressure of which can be regulated by the Screw J.
The underside of the cap A is provided with the tube K descending inside the
boiler to low-water level.
Fig. 4 is another modification of my improvements wherein the whistle valve E
is placed inside the inner tube D, the latter being provided at its top end with the

page_text: cap, head, or piston G in the whistle seat C, which also forms the seat of the valve;
the latter being held to its face by the spring I. In this arrangement the outer
tube B is provided with the holes L to allow access of atmospheric air to the outside
of the inner tube D for the purpose of cooling it or nearly so to prevent its full
expansion as long as water remains in it, thus allowing a greater range of
expansion when empty of water and steam is admitted. In the bell of the
whistle H is fixed the screw J for the purpose of regulation. When the apparatus
is fixed on the front of a boiler as in Fig. 1, the cap A is provided with the valve M,
as shewn in Fig. 5, for the purpose of shutting off the connection in case anything
goes wrong with either the boiler or alarm.
The apparatus is fixed as shewn in Figs. 1 and 2, so that the opening into it is
on a level with the low-water line, thus allowing the water when at working level
or above the opening N into the apparatus to enter and stand in the tube D.
When the water in the boiler descends and assumes what is known as the low-
water level, the inner tube D empties itself, when its place is taken by steam, which
raises the temperature of the tube D and expands it, with the result that it forces
the valve E off its seat, when steam is admitted, through the valve E in Fig. 4, or
through the holes T in Fig. 3, into the bell of the whistle H, by which the latter is
blown or sounded, which continues as long as there is steam in the boiler and the
water is at low-water level. In the modification in Fig. 4, the valve E rises with
the cap, head, or piston G secured to the expanding tube D, when the valve E is
forced off its seat by the stem coming in contact with the end of the adjusting
screw J, when steam escapes with the result before stated.
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
The respective combinations of the parts forming my improved modifications of
low-water alarm, wherein is used the internal expanding tube D, fixed in the
stationary cap or seat A, with the various modes of operating the valve E, the
whole being respectively constructed and operating substantially in the manner
described and as shewn on the drawings.
1
1005
EDMUND CHADWICK,
Agent for the Applicant,
92, St. George's Road, Bolton,