IMPROVEMENTS IN SAFETY APPARATUS FOR STEAM BOILERS
Year: 1878

page_text: LETTERS PATENT to Alfred Longsdon, of Queen Victoria Street, in the City of
London, for the Invention of "IMPROVEMENTS IN SAFETY APPARATUS FOR
STEAM BOILERS." A communication from abroad by Alfred Krupp, of Essen,
Prussia, Cast Steel Manufacturer.
*Sealed the 23rd May 1879, and dated the 26th November 1878.
PROVISIONAL SPECIFICATION left by the said Alfred Longsdon at the Office
of the Commissioners of Patents on the 26th November 1878.
ALFRED LONGSDON, of Queen Victoria Street, in the City of London. "IM-
PROVEMENTS IN SAFETY APPARATUS FOR STEAM BOILERS." (A communication from
abroad by Alfred Krupp, of Essen, Prussia, Cast Steel Manufacturer.)
Heretofore many attempts have been made to produce safety apparatus for steam
boilers with fusible alloys, but the contrivances hitherto employed as safety
apparatus for steam boilers have indicated the scarcity of water in such manner
that the alloy fuses or melts away when the temperature unduly rises, thus freeing
the orifice obstructed by the alloy, and the steam escaping indicates the scarcity of
water either by its noise or by its action on a whistle or other contrivance.
Now this Invention differs from others in that the alloy is shut up in a vessel in
which it fuses or melts when the temperature rises; thus obviating by reason of its
fluid state existing defects, so that a signal is given or appliances are brought into
action which influence the production of steam. In all cases there is no loss of
alloy; on the contrary, the same metal can be used over and over again, and the
apparatus resets itself.
The Invention may be conveniently carried into effect as follows:-According to
one arrangement the alloy is placed in a valve which can be pressed strongly upon
its seat by a screwed cap or a screw passing there through, the pipe leading to
the valve being so arranged that the temperature of the water in it will not melt
the alloy; the valve can be shut by pressure on the solid alloy by means of one of
Price d

page_text: the screws aforesaid; but in the event of the alloy melting in consequence of
scarcity of water the pressure ceases, the valve rises, and the escaping steain signals.
The alarm apparatus is shut by screwing the cap down, after which the screw is
raised sufficiently to get out of contact with the alloy, the latter having become set,
the shutting of the valve is again effected by the same screw, which has first to be
screwed down strongly and afterwards clinched until the cap has been raised, after
which the apparatus is set and ready for further signaling purposes.
According to another arrangement the fusible alloy is shut up or enclosed in a
box which is tightly jointed or screwed on to the steam pipe, and in all instances
the alloy, when hard, arrests or holds a piece of mechanism which, when the alloy
gets fluid again, is released to produce a signal; for example, a rack or ratchet
wheel may be used, one tooth of which is cast or inserted in the alloy, whilst a
tension is created on another tooth either by means of the raised damper or the cut
off valve of a gas pipe or a ringing apparatus, a steam signal, an electro magnet, or
any other suitable arrangement. If the alloy melts the ratchet wheel is released.
The damper shuts the flue to chimney, the gas flow ceases, and the bell, whistle, or
other signal sounds; various contrivances may be devised for acting in a similar
manner, being held in the alloy while it is hard, and released when fused or partially
so; for example, the holding appliance may be a bar with enlarged end going into
the alloy, and in another instance the bar may be merely placed on top of the
alloy. In the first instance the bar is released by rising out of the alloy, and in
the second by dipping into the same; but the inventor does not limit himself to
any special form of the whole contrivance provided the essential features of the
Invention are retained, which are:-The use of easibly fusible alloys or substances
in vessels, saucers, caps, or pipes, for the purpose of indicating the scarcity of water
in steam boilers in such a manner that as soon as the alloy fuses the piece retaining
the signal or cut off contrivances is released, and the alloy is not lost; but in one
instance it dips down into the alloy, in another it rises out of it, and in a third it
revolves or oscillates in it, and the apparatus resets itself as the alloy hardens.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Alfred Longsdon in the Great Seal Patent Office on the 26th May
1879.
ALFRED LONGSDON, of Queen Victoria Street, in the City of London. "İM-
PROVEMENTS IN SAFETY APPARATUS FOR STEAM BOILERS." (A communication from
abroad by Alfred Krupp, of Essen, Prussia, Cast Steel Manufacturer.)
Heretofore many attempts have been made to produce safety apparatus for steam
boilers with fusible alloys, but the contrivances hitherto employed as safety
apparatus for steam boilers have indicated the scarcity of water in such manner
that the alloy fuses or melts away when the temperature unduly rises, thus freeing
the orifice obstructed by the alloy, and the steam escaping indicates the scarcity of
water either by its noise or by its action on a whistle or other contrivance.
Now this Invention differs from others in that the alloy is shut up in a vessel in
which it fuses or melts when the temperature rises, thus obviating by reason of its
fluid state existing defects, so that a signal is given or appliances are brought into
action which influence the production of steam. In all cases there is no loss of
alloy; on the contrary, the same metal can be used over and over again, and tho
apparatus resets itself.
The Invention may be conveniently carried into effect as follows:-According to
one arrangement the alloy is placed in a valve which can be pressed strongly upon
its scat by screws, the pipe leading to the valve being so arranged that the tempe-
rature of the water in it will not melt the alloy.
Figure 1 of the accompanying Drawings is a vertical cross section, and Figure 2
is an external elevation of a safety apparatus or fusible plug for steam boilers
constructed according to this arrangement. A is the alloy; B, the valve in which
the alloy is placed; E, the valve seat; C and D are the screws for operating on the
valve B; F, the water pipe. The valve B can be shut by pressure on the solid
alloy A by means of the screw D; but in the event of the alloy A melting in
consequence of scarcity of water the pressure ceases, the valve B rises, and the
escaping steam signals.
The alarm apparatus is shut by screwing the screw C down, after which the other
screw D is raised sufficiently to get out of contact with the alloy, the latter having
become set, the shutting of the valve B is again effected by the same screw D,
which has first to be screwed down strongly and afterwards clinched until the other
screw C has been raised, after which the apparatus is ready for further signalling
purposes. According to another arrangement the fusible alloy is shut up or
enclosed in a box which is tightly jointed or screwed on to the steam pipe, and in
all instances the alloy when hard arrests or holds a piece of mechanism which, when
the alloy gets fluid again, is released to produce a signal; for example, a rack or
ratchet wheel may be used, one tooth of which is cast or inserted in the alloy,
whilst a tension is created on another tooth either by means of the raised damper
or the cut off valve of a conduit of gas, or a ringing apparatus, a steam signal, an
electro magnet, or any other suitable arrangement.
Figure 3 is a vertical cross section, Figure 4 is an external side elevation, and
Figure 5 is a plan of apparatus constructed according to this arrangement. A is
the fusible alloy; B is the box or valve in which the alloy is placed; G, the ratchet
wheel on the spindle H, a tooth or teeth of which is embedded in the alloy as
shown; and F is the water tube, as before. Figures 6, 7, and 8 show in vertical
and horizontal section and plan respectively an arrangement where the ratchet
wheel is embedded in the alloy. If the alloy A melts the ratchet wheel G is
released. The damper cuts the channel off from the chimney, the gas-flow ceases,
and the belt, whistle, or other signal sounds; various contrivances may be devised
for acting in a similar manner, being held in the alloy while it is hard, and released
when fused or partially so; for example, the holding appliance may be a bar with
enlarged end going into the alloy.

page_text: Figure 9 is a vertical cross section of an apparatus made according to this
arrangement.
Figure 10 is
vertical cross section, and Figure 11 is a plan of an arrangement
where the bar merely rests on the alloy. In Figure 9 the bar is released by rising
out of, and in Figures 10 and 11 by dipping into the alloy; but the inventor does
not limit himself to any special form of the whole contrivance provided the essential
features of the Invention are retained.
Having now described the nature of the said Invention, and in what manner the
same is to be performed, I declare that I claim as the aforesaid improvements in
safety apparatus for steam boilers,—
First. The employment or use in such apparatus of easily fusible alloys,
substances, or compositions contained in vessels or receptacles for the purpose of
indicating scarcity of water in steam boilers in such manner that as soon as the
alloy fuses the piece or pieces, appliance or appliances retaining the signal or cut off
contrivance or contrivances is or are released a signal is made, and at the same time
the alloy is not lost, but can be used over and over again, all substantially as
hereinbefore described, and illustrated in the accompanying Drawings.
Second. The particular apparatus and appliances, together with any mere
modification thereof, for containing fusible alloys, all constructed and operating
substantially in manner and for the purposes hereinbefore described, and illustrated
in the accompanying Drawings.
.
In witness whereof, I, the said Alfred Longsdon, have hereunto set my hand
and seal; this Twenty second day of May, in the year of our Lord One
thousand eight hundred and seventy nine.
ALFRED LONGSDON. (L.S.)