Improved Electrical Low Water Alarm or Indicator for Steam Boilers.
Year: 1896

page_text: Date of Application, 18th Dec., 1896
Complete Specification Left, 18th Oct., 1897-Accepted, 18th Dec.,
1897
PROVISIONAL SPECIFICATION.
Improved Electrical Low Water Alarm or Indicator for Steam Boilers.
THOMAS HUGHES Engineer 22, Heygate Street Walworth, London S.E. do
hereby declare the nature of this invention to be as follows:-
This invention relates to a certain new or improved electrical alarm for Steam
Boilers, to indicate low water level and in carrying the invention into effect I
proceed as follows:-
A thin steel, iron or composition metal tube is provided as a mercury holder.
said tube being closed at its lower end and fastened at the other end into a screwed
brass or iron cover, said cover being screw threaded.
The said screw cover carries two terminal buttons for wires of an electrical
circuit, one of the said wires being shorter than the other and both being led into
the tubular mercury holder.
This cover screws into or upon an iron, brass, or gun metal casing which is in
turn provided, with a screw threaded union piece to be screwed into the crown of
the Boiler, said union piece of the main casing being fitted at the lower end with
a metal tube projecting for required distance into the Boiler, below the water
level.
When the water level falls below the end of this tube steam will take its place
and the higher temperature will cause the mercury to expand and reach the
shorter terminal wire of the electrical circuit, thus completeing same and sounding
the alarm bell or bell's, or other signal in connection to give warning or indication
at one or more points.
Dated this 18th dow of December 1806
COMPLETE SPECIFICATION.
Improved Electrical Low Water Alarm or Indicator for Steam Boilers.
I THOMAS HUGHES, Engineer, formerly of 22 Heygate Street, Walworth,
London, S.E but now of 2 Emery Street, Westminster Bridge Road, London, S.W.
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 a certain new or improved electrical alarm for steam
boilers, to indicate low water level and failure of water supply.
In the following description reference will be made by figures and letters to the
accompanying drawings; wherein, Fig. 1, is a vertical elevational. section of a
construction according to this invention showing the "expansion-metal" holder

page_text: and electrical connections detached from the hollow-body and its water and steam
tube.
Fig. 2, is a like view but with the cover and steam and water casing and tube in
position, the expansive metal holder being of modified form to contain a fusible
alloy for setting-up electric contact by the expansion when the heat rises above
the normal.
Fig. 3, is a top view with portion of the dome of the cover shown broken away,
the electrical connections and cap being shown in solid and dotted lines.
Fig. 4, shows in vertical sectional view detail of fitting of the expansion metal
tubular holder with a metal coil or spiral for effecting the electrical contact and
closing of the "circuit" upon increase of heat above the normal.
A, represents portion of the shell, of the crown or front, of the boiler. The
body a, of the apparatus is hollow and the lower extremity is screw threaded at a',
externally, and also internally at a. The portion a³, of the body is formed as a
nut for purpose of "screwing-on" to the boiler, and on to the tube b, said tube being
of length, determined upon, and requisite for extending into the boiler below the
normal or safe water-level.
The upper end of the body a, is internally screw-threaded at a', to receive the
lower screw-threaded end of the nipple c, said nipple being screw-threaded exter-
nally at ; and intermediately of the portions c, and c', is a nut c².
Into the nipple c, is brazed or soldered the upper end of the tube d, said tube d,
serving as the container of any metal or metal alloy which will by expansion, due
to increased heat of the steam cause contact to be made or effected with an electric
circuit.
As shown in the drawings a platinum wire e, is carried by the electrical terminal
button f, which is put in circuit as will next be described, the same purpose being
served whether the tube terminates with a bulb d containing mercury as in Fig. 1;
or, again, if a spherical bulb d², containing fusible alloy be employed, as shown in
Fig. 2; or, again, if a spiral, or other form, of metal metal, which will sufficiently
expand when the heat is raised or is excessive, be employed within the tube d, care
always being taken that whilst the requisite contact be effected between the wire e,
and the contact metal so expanded, the wire e, shall in no case, of itself, come in
contact with the tube d.
The insulation and carrying of the contact wire e, is effected conveniently as
shown by the drawings, that is: The cap g, is internally screwed for attachment
to the nipple screw c¹, and formed, externally, as a nut." The interior hollow of
cap g, is extended beyond the screwed portion to receive insulating material g²,
and above this is an opening or slot of dimensions such as will allow of the
screw of the electrical terminal f, being screwed into the insulation material with-
out admitting of the said terminal f, making or suffering contact with the metal
of the cap g.
Into the metal of cap g, is screwed or applied the terminal h (to
earth) of the circuit the wires being connected up with the battery or source of
electric supply, and the electric bell, gong, or other alarm being also put in cir-
cuit, secundum artem, as may be required to notify failure of the water supply at
any one or more points of indication as would be readily carried-out by anyone
acquainted with the fitting of such like devices.
In the case of an expansion metal being used to make contact between same and
the terminal f, it will not require that the said terminal f, be attached to the
wire e, and an illustration of this is shown by Fig. 4:-In this case the expansion
metal may be in spiral form such as shown, and a copper wire may be advan-
tageously used. The tube d, is closed at d³, the lower end of the spiral being fixed
thereto (the convolutions of the spiral are of dimensions to fit loosely within the
tube d, but so as to prevent sidewise flexion). The tube d, has a plate or bridge d'
secured at the upper extremity thereof and has a central orifice which will serve
as a guide. The upper end e', of the spiral is straightened and led through the
orifice, and will be of length sufficient to allow of vertical play therethrough and

page_text: so that upon accession of heat and expansion of the spiral the continuation e¹, will
be extended to meet the end of the terminal f, thus completing the circuit.
The tube d, will be attached to the nipple c, substantially as before described in
reference to Figs. 1 and 2.
The safety lock-cover shown in Figs. 2 and 3, consists of a cylindrical cover i,
with top plate k, having holes therein through which the circuit wires are carried.
At the bottom of cylinder i, is a strap terminating in pierced ears 7. A projecting
pin a5, is fitted to the body a, and a vertical slot i, of cylinder i, will allow of the
cylindrical cover i k, assuming position, shown in Fig. 2, with the ears 1, and pad-
lock, such as m, below said pin a, to prevent the cover i k, being removed and pre-
venting the circuit terminals being interfered with accidentally or otherwise
except by the person in charge.
In use, when the boiler is heated to proper degree and the normal or safe water
level is maintained the existing pressure will cause the water to fill into the tube b,
and the internal hollow of the body a, and the "setting" of the apparatus will
leave the circuit-contact uncompleted. When however the proper or safe level of
water falls below the free end of tube b, the internal space of body a, will become
open for the accession of steam which exceeds that of the water-normal-heat, the
expansion metal will become dilated in tube d, and the contact will be made
between same and the wire e, so establishing the electric circuit between the two
terminals to effect the signal in connection, and the alarm will continue until
attention has been given to the boiler supply.
Having now particularly described and ascertained the nature of my said Inven-
tion and in what manner the same is to be performed, I declare that what I claim
is:-
First. The improved low water alarm apparatus as herein set forth, constructed
combined and operating as and for the purpose herein described in reference to
and shown by the drawings.
Secondly. In a low water alarm as herein set forth the tube b, connected with
the hollow water and steam space of a hollow body, such as a, combined with the
expansion metal tubular-container, such as d, as and for the purpose herein
specified.
Thirdly. In a low water alarm apparatus as herein set forth, the combination
of a water and steam tube b, body a, expansion metal tubular-container e, the
nipple union-piece such as c, cl, cap g, g', with insulating material and terminal f,
as and for the purpose herein set forth.
Fourthly. In combination with a low water alarm, as set forth, the safety
cover i kl and the stop piece a, of the body a. and a locking device substantially
as set forth.
Dated 18th Oct 1897
WALTER A. BARLOW
For the Applicant 306 High Holborn W.C.