A NEW OR IMPROVED APPARATUS FOR PREVENTING THE EXPLOSION OF BOILERS OR GENERATORS OF STEAM
Year: 1837

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
PIERRE DEVAUX, of Fenchurch Street, in the City of London, Merchant, send
greeting.
WHEREAS His late most Excellent Majesty King William the Fourth, by
Ilis Royal Letters Patent under the Great Seal of Great Britain, bearing date
at Westminster, the Twenty-third day of May, in the seventh year of His reign,
and in the year of our Lord One thousand eight hundred and thirty-seven,
did, for Himself, His heirs and successors, give and grant unto me, the said
Charles Pierre Devaux, His especial license, full power, sole privilege and
authority, that I, the said Charles Pierre Devaux, my executors, administrators,
and assigns, or such others as I, the said Charles Pierre Devaux, my execu-
tors, administrators, or assigns, should at any time agree with, and no others,
from time to time, and at all times during the term of years therein mentioned,
should and lawfully might make, use, exercise, and vend, within England,
Wales, and the Town of Berwick-upon-Tweed, an Invention of "A NEW OR
IMPROVED APPARATUS FOR PREVENTING THE EXPLOSION OF BOILERS OR GENERATORS
OF STEAM," being a communication from a Foreigner residing abroad; in
which said Letters Patent is contained a proviso obliging me, the said
Charles Pierre Devaux, by an instrument in writing under my hand and seal,
particularly to describe and ascertain the nature of the said Invention, and in
what manner the same is to be performed, and to cause the same to be
inrolled in His Majesty's High Court of Chancery within six calendar months
next and immediately after the date of the said in part recited Letters

page_text: Patent, as in and by the same, reference being thereunto had, will more fully
and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Charles Pierre Devaux, do hereby declare that the nature of the said Inven-
tion, and the manner in which the same is to be performed, are particularly
described and ascertained in and by the following description thereof, refer-
ence being had to the Drawing hereunto annexed, and to the letters and
figures marked thereon (that is to say):
Whereas the explosions of boilers or generators of steam arise sometimes
from the steam simply accumulating gradually in the boiler or generator
until it has acquired an elastic force, exceeding in intensity the force of resist-
ance of the metal of the boiler or generator, and more frequently from the
level of the water in the boiler or generator being suffered to get low enough
to allow the sides of the boiler or generator to become heated to a very high
temperature, whereby, when a fresh supply of water is introduced into the
boiler or generator, and comes suddenly in contact with the over-heated sides
thereof, the sudden formation of a great volume of steam takes place; and this
overheating of the sides of the boiler takes place sometimes in marine boilers
from the vessel lying over for a considerable time on either side, by which the
opposite side of the boiler is left unprotected by water; and sometimes
explosions arise from the sudden opening of a valve or of any other aperture
in a boiler, whereby, in consequence of the sudden diminution of the pressure
upon the surface of the water a violent ebullition of the water is produced,
dashing it about in the boiler as well all over the space occupied by the steam
as against the top and sides of the boiler; and then, if the level of the water
has been suffered to get low enough for the sides of the boiler to have become
over-heated, or if by accident any parts of the boiler have become so overheated
so as to surcharge the steam with caloric, then the water coming suddenly in
contact with the said over-heated surfaces of the boiler, or into the midst of the
steam surcharged with caloric as aforesaid, will be converted suddenly into a
great volume of steam; and sometimes such explosions may takes place in
consequence of the formation of saline or earthly or calcareous incrustations or
deposits upon the bottom of a boiler or generator; for such incrustations or
deposits being bad conductors of heat, may allow the bottom plates of the
boiler or generator to acquire a very intense heat without the same being
immediately or regularly transmitted to the water, until at length the heat
becomes sufficient to break up or disturb the said incrustations or deposits, and
then the water coming in sudden contact with the over-heated plates, a sudden
generation of a great volume of steam will take place; and sometimes also

page_text: such explosions arise from another cause, (viz.)-It sometimes happens that
caloric accumulates in the water contained in the boiler or generator instead
of converting the same regularly into steam, and when the water becomes thus
charged with caloric beyond a given point, the caloric suddenly disengages
itself and a very great volume of steam is generated. Now, the object of the
said new or improved apparatus for which the said Letters Patent have been
granted to me as aforesaid, is to preserve boilers or generators of steam from
the effects of the aforesaid causes of explosion. And it consists of several
parts (that is to say):-One part of the said new or improved apparatus which is
intended chiefly to obviate the danger of explosion arising from a simple gradual
accumulation of steam in a boiler or generator, is a compound safety valve or
safety apparatus composed of a safety valve of the ordinary construction,
(loaded by means of a weight hung on the end of a lever), combined with a
loaded plunger or piston working in a cylinder filled with oil or other fluid,
into which cylinder steam is admitted from the boiler or generator to press on
the surface of such oil or fluid, and raise the plunger or piston whenever the
first or ordinary safety valve does not act freely and correctly, so as to lift up
such first safety valve and insure the escape of the superabundant steam, the
said first safety valve being capable of acting independently of the said piston
or plunger so long as it is in proper order.
And another part of the said new or improved apparatus is intended to
prevent the danger of explosion arising either from the presence of steam too
highly elastic in the steam space of the boiler, (whether the same proceed from
a gradual accumulation or from any sudden generation of steam), or from
the accumulation of heat in the water, or from the heating of the bottom of
the boiler by reason of incrustations or deposits. Or in some particular cases
the said part of the said apparatus is more particularly adapted to prevent the
evil effects which would follow the level of the water being suffered to sink
too low. And the said part of the said apparatus consists of a combination
of pipes, steam boxes, cocks, and other parts in which a piece of fusible
metal is applied, adapted to melt at a given temperature. And such fusible
metal is applied either to be acted upon by the heat of the steam in the
upper part of the boiler, or by the heat of the body of water in the lower part
of the boiler, or by the heat of the bottom part of the boiler, or by the heat of
the furnace applied to a conductor of heat herein-after described, according as
the object of this part of the apparatus is to prevent explosions arising from a
sudden or other formation of too highly elastic steam in the steam space, or
from a heating of the body of the water, or from a dangerous heating of the
bottom or sides of the boiler, or from the level of the water subsiding too near

page_text: the bottom of such boiler; and the effect of the melting of the fusible metal is
to open an exit passage for the steam contained in the boiler, which exit can
be checked at pleasure so as to allow the melted fusible metal to be replaced
by another piece of such metal without interrupting the working of the engine,
as I will hereafter more minutely describe.
And another part of the said new or improved apparatus is an improved
float apparatus, adapted not only to indicate the level of the water in the boiler
or generator, but to allow the escape of steam when that level sinks too low.
And lastly, another part of the said new or improved apparatus which is
more particularly applicable to steam boat boilers, consists of dampers adapted
to operate by their own gravity, or by the gravity of other heavy bodies,
whenever a steam boat lies over on one side for any length of time, so as to
close partially or wholly the passage through the flues or chimney, as I will
berein-after describe more minutely; and note, the steam allowed to escape from
the boiler or generator by the operation of any part of the aforesaid apparatus
is carried in the manner herein-after more minutely described, either into the
flues which surround the boiler or generator in a direction opposite to that of
the draft of the furnace, for the purpose of. driving the hot air and flame back
towards the furnace so as to wholly or partially destroy the effect of the fire; or
such waste or superabundant steam may be carried direct into or under the
furnace, partially or wholly to extinguish the fire; or it may be employed in
other modes, as I will herein-after mention, for the purpose of giving notice of
danger to the persons having charge of the engine; or lastly, it may be allowed
to escape into the atmosphere. And all the parts of the said new or improved
apparatus may be combined in the same boiler, as they may be used separately
according to circumstances, as I will hereafter more minutely explain.
I will now proceed to describe the construction of the several parts of the
said new or improved apparatus in reference to the sheet of Drawings here-
unto annexed, on which the same letters indicate corresponding parts.
Figures A, B, and C represent a steam boiler to which the greater part
of the said new or improved apparatus is applied. The other Figures represent
the different parts of the said apparatus in detail. Figures 1 to 6 represent
that part of the apparatus which consists of a compound safety valve or
safety apparatus. Fig. 1 is a side view thereof (taken at the line 1, 2, Fig. 3),
seen in a box or case in which the same is to be placed and locked up; the
case is shewn in section. Fig. 2 is a vertical section of the compound safety
valve, taken through the centre line 3, 4, of the plan Fig. 3. Fig. 4 is
a cross section of part of the compound safety valve; and Figures 5 and 6
are detached views of parts of the same. a to h, Figures 1 and 2, are parts

page_text: nearly similar and corresponding in operation to the parts of the ordinary
loaded safety valve (that is to say), a is a cylindrical pipe communicating with
the interior of the boiler. At the upper end of the pipe a is the seat for
the valve b, the stem c of which passes freely through a cup in the upper part
of the valve box d, and the said valve is loaded by means of a weight e fixed
near the extremity of a long lever f, which turns on a fixed centre pin mounted
in a standard g, and is linked to the stem c of the valve b, by means of a short
link h, the lower end of which rests on the top of the stem c, and a pair of other
short links P, which catch under projecting ears at the upper end of the stem c,
see Fig. 5, which is a section of the link and upper part of the stem c; by this
means, if the outer end of the lever f be pressed down, it will press the valve b
down in its seat, but if the lever be lifted up the valve will be also lifted up by the
suspending links p. The lever f is guided in a grooved bracket i, see Figs. 1
and 2. The extreme end of the lever f has a forked formed on it, out
of which two short pins project which enter into openings in the lower ends of
the pair of vertical links ; the upper ends of those links are jointed to a
rod, the lower end of which is cased in a tube of hard steel or glass fitted
tightly on the said rod, so as to form a plunger or piston, which works through
a collar of leathers in a cylinder m, being pressed down to the bottom thereof
when the apparatus is at rest by a weight v. The cylinder m communicates
by a horizontal passage with a small cylinder n, see Figures 3 and 4. Both
of these cylinders are filled with oil or other fluid, and the small cylinder n
communicates by a pipe o with the tube a beneath the valve b, sce Fig. 2.
It should be observed, that when the apparatus is at rest, the valve 6 being in
its seat, the pins of the lever f that enter into the openings of the links K
do not rest on the bottoms of the said openings of the links K, but that
it would be requisite to lift up the rod 7 a little before the said links would
take up the lever f by its pins. Now the operation of this apparatus is as
follows:-If the steam in the boiler rise at all above the pressure, of which the
pressure exercised upon the valve b by its weight e is the measure, it will lift
up the valve (provided that the valve is in good order), and passing by its
edges into the valve box d, will escape through the pipe g which leads it
away into the atmosphere (or into the flue or furnace for the purpose herein-
after mentioned). But if, as is often the case with safety valves, the valve b
should either from oxydation or from the external pressure of the atmosphere,
or from any other cause, stick in its seat and not rise readily when the steam
exerts against its under surface the pressure at which it is calculated to be
lifted up, then the steam continuing to accumulate in the boiler, and which
fills the pipe o, and is in contact with the surface of the oil contained in the

page_text: cylinder n, will exert its pressure thereon, and thus cause the plunger or
piston 6 to rise. When the said plunger has risen a little way, the bottom
of the openings of the links K will catch against the pins of the fork at the
end of the lever f, and lifting up the end of that lever will thereby lift up the
valve bout of its seat. And it is to be observed that the piston b acts with a
greater force to lift the valve 6 than is due merely to the increased pressure of
the steam, because it acts with a very long leverage on such valve; the
valve b, therefore, will thus be compelled to rise before the steam has acquired
a dangerous intensity of elastic force. And note, the force transmitted by the
plunger to the valve b may be still further increased, if desired, by increasing
the area of the plunger or piston, as compared with the area of the cylinder n,
on the principle of the hydraulic press. As soon as the valve b quits ifs seat
steam will get by the edges of the said valve, and consequently the pressure
on the surface of the oil in the cylinder n will immediately begin to diminish;
and as more and more steam escapes through the valve b, the pressure on the
surface of the said oil tending to force up the piston l, will more diminish, so
that the piston or plunger will gradually descend and cease to operate upon the
valve b. It will be now easily understood that the effect of this combination
of parts is not only to cause the valve 6 to be forcibly lifted, as aforesaid,
whenever it does not yield to the direct pressure of the steam, but to
regulate its motion and prevent it from jumping up suddenly and then
suddenly falling, as is often the case with ordinary safety valves, because the
valve cannot rise much unless the steam is strong enough to act upon the
plunger, and the motion of that piston will not diminish instantaneously, but
must have time whereby the changes of motion of the valve b will be compelled
to be gradually effected. For the diameters of the cylinders m and n, the
size of the weight v, and its distance from the centre of the lever f, no precise
rule can be laid down; they must be regulated according to the maximum
pressure which it is safe to allow the steam to acquire in the boiler. The
whole apparatus is contained, as already mentioned, in a box A, which will be
furnished with a proper door and lock and key, and the said box should be
kept locked and the key kept by the person having charge of the engine in
chief, so as to prevent any tampering by the workmen with the load of either
the first valve or of the piston 7. The box A may stand over any suitable
part of the boiler, detached therefrom as at A in Figures A and B. Note,
in those Figures an ordinary safety valve is drawn at (y), and a branch pipe
is connected therewith, to which the pipe a of the compound safety valve
may be connected to introduce steam from the boiler into the said compound
safety valve. The pipe 9 is shewn in Figures 1 and 2 broken off.. It leads

page_text: the superabundant steam into the atmosphere, as shown at q, Fig. A. As to
that part of the said new or improved apparatus, the operation of which
depends upon the melting of a piece of fusible metal, such fusible metal may
be applied either at or near the bottom of the boiler to receive heat from the
mass of heated water and from the metal of the bottom of the boiler and from
steam brought into contact with the said plug of fusible netal; or else
such fusible metal may be applied at the upper part of the boiler, so as to he
acted upon only by the heat of the steam itself in such upper part; or other-
wise, it may be applied so as to be acted upon through conductors of heat.
which I will hereafter describe, to allow an escape of steam, either whenever
the level of the water has sunk too near the bottom of the boiler, or whenever
the bottom of the boiler is acquiring too high a temperature. Figures 7 to 14
represent the first mode of applying the fusible metal; and Figures 15 to 18.
represent the second mode of applying it; and Figures 19 to 24 represent the
third mode of applying it. Fig. 7 is a vertical section; Fig. 8 is an outside
view; Fig. 9 is a plan, and Fig. 10 an horizontal section taken at the
line 1, 2, Fig. 7; Fig. 11 is a vertical section taken at the line 3, 4, Fig. 8;
Fig. 13 is a horizontal section taken through the line 5, 6, Fig. 7; Fig. 14 is
a plan of the cover p. a, a, b, b, represent the top and bottom plates of a
boiler; c is a box firmly fixed to the bottom plate of such boiler. From the
box two pipes d and e rise, which are fitted with steam-tight joints
respectively to the box c and the top plate of the boiler, see Figures 7 and 8.
In the pipe d is placed another pipe f, fitted into the top part of the pipe d
with a screw joint (see the upper part of Fig. 7). The upper end of the
pipef has an open communication with a steam box g, from which a pipe h
leads into the flue of the furnace, see Figures A, B, and C, before mentioned.
The box is closed by a cover p fastened on it steam tight. The fastening
of the said cover is effected by means of two ears growing out of it, which fit
into cavities formed in the two upright standards q; when the said ears are
within such cavities the cover cannot be lifted up but by turning the cover
round so as to turn the said ears out of the cavities; the cover can be lifted up
from the box g, the standards q rise from the box g, see Fig. 12, and a
horizontal rod passes through them and through the square at the top of
the cover, see also Fig. 12. On one end of the rod z a padlock fis fastened,
which, being locked, the rod z cannot be drawn out, and consequently the
cover p cannot be removed. The tube e communicates through a small tube i
in which a stopcock is fitted at 7 to a bent tube m which turns down through
the top plate of the boiler, and has fitted over its end a cap n pierced with
small holes. And note, the rod z also passes through a lever handle which

page_text: is fitted on the square of the stopcock /, so that by keeping the padlock
aforesaid locked the lever handler and stopcock will be retained in the
positions shewn in the Drawing. When the apparatus is set for working
the stopcock is set and kept open, as shewn in Fig. 7, to allow steam to
pass from the boiler into the tube c. The lower end of the pipe f is slightly
conical, and into the conical part is fitted a small plug of fusible metal, which
may be composed of lead, tin, and bismuth; the proportions in which these
three metals will be combined will depend, of course, upon the temperature
at which the fusible plug is intended to melt. The interior of the seat of
the plug of fusible metal is tinned, in order to prevent oxidation of the fusible
metal. Over the lower end of the pipe f is screwed a small cover or box, with
a central stem to support the plug of fusible metal, see Fig. 7, and small holes
are pierced in the sides of the said cover, to allow steam to pass into it from
the pipe e, and to come in contact with the plug. The operation and effect of
this, apparatus are as follows:-When the boiler is in operation the box c,
resting, as aforesaid, on the bottom of the boiler, and being surrounded by the
liquid mass of water, will gradually acquire the same temperature as the water
which surrounds it, and that temperature will, by degrees, be transmitted to
the plug of fusible metal while steam is being generated; a portion of such
steam entering through the cover n of the pipe m, will pass along that pipe and
through the cock (which is set open, as aforesaid, when the boiler is at work),
and will flow through the pipe e, and enter the box c. The steam meeting
with no aperture for its escape, and consequently being motionless, will rise to
the same temperature as the metallic surfaces which contain it, which are them-
selves at the same temperature as the surrounding water and as the bottom of
the boiler respectively. The under part of the fusible plug will thus be in con-
tact with steam, the heat of which tends, in conjunction with that of the
metallic surface of the lower plate of the boiler of the box c, and pipes d and f
to melt it. As long as the heat of the steam keeps within the prescribed
limits, or as long as the liquid mass of water does not reach a temperature
exceeding that at which the fusible plug is calculated to melt, things will
remain in this condition of rest, and no effect will be produced by the apparatus.
But if there should be produced an excess of heat in the steam, or an excess of
heat in the lower part of the mass of water contained in the boiler, or in the
bottom of the boiler, whether by reason of incrustations or deposits, or by any
other cause, then such heat will melt away the bottom and part of the sides of
the fusible plug, which, therefore, no longer fitting tight in its seat, will be
blown by the stean up through the pipe finto the stean chamber g, and the
superabundant steam, rushing up that pipe into the said steam chamber, will

page_text: be thence conveyed through the pipe h and the guide (a), see Fig. A, into the
flue surrounding the boiler in a direction contrary to that of the draft coming
from the furnace. The fire will thus be damped in its action in proportion to
the length of time during which the discharge of steam is continued, and thus
the boiler, instead of getting more heated, will, on the contrary, become pro-
gressively cooler in its whole extent. When the fusible plug has melted, the
escape of steam may be stopped as soon as deemed necessary, without stopping
the engine. For this purpose the padlock must be removed from the rod,
which will be withdrawn, and the lever handle r must be raised up so as to
bring the cock round to close the passage through the pipe i, which will stop
the escape of steam, see Fig. 7; the cover p will then be removed, and any par-
ticles of the fusible metal which may have fallen and remained in the
chamber g, be cleared out. The pipe f is then taken out, and the cap or box
will be taken off from the lower end of the said pipe f, and after clearing out
of of the said cover any remaining particles of the fusible metal, a new fusible
plug is put into the end of the said pipe. Note, the plugs of fusible metal
should be made a number at a time in moulds corresponding to the end of the
pipe, so that any plug taken without selection from the store will fit such pipe.
This plug is put in its conical seat, and with a blow of a hammer will be driven
thercin quite firmly and steam-tight. After the fresh plug has been put in
the cap or cover of the lower end of the pipe f will be screwed on again, and
the said pipe put back in its place in the pipe d, the cover p will be then
fastened down, the cock 1 set open, as in Fig. 7, the rod z will be put through
the lever handle in its place to retain the cock open, and the padlock
fastened on again and locked. All the parts will now be again in the position
shewn in Fig. 7, and ready again to operate to prevent explosion. Note, for
greater security the cover p may be fastened to the fixed part of the tube b, by
means of a padlock, of which the engineer in chief may keep the key; but I
have shewn such parts on the Drawing. In Figures 15, 16, 17, and 18,
(which represent, as aforesaid, an apparatus acting by means of a fusible metal
plug applied at the upper part of a boiler, to be acted upon only by the heat of
the steam itself); Fig. 15 is a transverse section; Fig. 16 an outside view;
Fig. 17, a horizontal section taken at the line A, Fig. 15; and Fig. 18 is a
plau of Fig. 16. a, a, in all the Figures is the upper plate of the boiler; b is
a short tube firmly bolted to the boiler, the lower part of which tube is inside
of the boiler, and serves as the seat of a cock, while the upper end of the said
tube b, which is of larger diameter, forms a steam chamber. The flange of the
tube b, by which it is bolted to the boiler, must, of course, form a steam-tight
joint therewith; c is the conical plug of the cock, ground into the seat b; the

page_text: A
large end of the conical plug c is the lower end thereof, in order that the
pressure of the steam may tend to make the said plug fit tight in its seat. The
passage of the cock is double (see y, Fig. 15), opening horizontally into a
box d, which is perforated with holes, see Figures 15 and 16, and a vertical
cylindrical hole is bored out of the plug of the cock itself, see also Fig. 15,
in which is inserted the short upright pipe f, which corresponds to the pipe f
of the apparatus before described. In the lower end of this pipe is fixed, quite
steam-tight, the fusible metal plug. And note, when this part of the apparatus
is applied to a boiler, in conjunction with the part next herein-before described,
the fusible metal plug should be of an alloy adapted to melt with less heat than
the fusible metal plug of such former described part of the apparatus.
cover is placed over the chamber b, and can be fastened down tight thereon
by means of the claws q. which catch under the two semi-flanges 2, which are
made with slightly inclined planes on the under sides, that by turning the
cover p round by a key applied on the square f to the right or to the left, the
cover 2 can be drawn down tight upon the chamber b, or brought round into
such a position as to place the claws in the open spaces t, and then the
cover p can he lifted off. A circular horizontal plate æ is formed within the
cover p, with a short hexagonal neck descending from it to fit over the upper
end of the plug of the cock, (which is made hexagonal for the purpose of turn-
ing it round by means of the said cover p), and holes are made in the said plate,
see Fig. 17, to establish a communication between the chamber b and the
cover p, and make them in effect one steam chamber. A small cup vis
formed at the lower part of the box d, in which is placed a spiral spring, which
presses a small pin against the under side of the plug of the cock c, and
prevents its descending by its own weight. The effect and operation of this
apparatus are as follows:-Whenever the body of steam contained in the boiler
rises to a temperature and pressure exceeding those for which the boiler is
calculated, the different metal surfaces of the apparatus contained within the
boiler will gradually acquire the same temperature, and the heat of the said
surfaces, together with that of the steam which enters through the passages y,
and comes in contact with the plug of fusible metal, gradually melt the same
at the under side and edges, and then the steam will blow the plug up through
the pipe finto the steam chamber b, and by that means, a passage being cleared
for the steam, it will rush through the said pipe finto the steam chamber
above the perforated plate mentioned, and down through the holes in the said
plate, filling the steam chamber b, and thence passing into the pipe h, which
may lead it away into the atmosphere or into the flue surrounding the boiler,
to meet and check the draft of the furnace in the manner already described.

page_text: in speaking of parts of the apparatus already described. When the apparatus
has operated as aforesaid, the cover p will be turned round a quarter of a turn,
by which means the passages y will be shut, and the claws of the cover p.
being opposite the spaces t, as aforesaid, the said cover can be removed, the
tube f can then be taken out and (as well as the steam chamber) cleared of
any parts of the metal of the fusible plug which may be remaining in it, and
a new metal plug fixed in, in the same manner as I have described in reference
to the former apparatus. And note, the closing of the passages y stops the emis-
sion of steam from the boiler, so that the several parts mentioned may be taken to
pieces and replaced, without stopping the working of the engine. In Figures 19
to 24 other modifications of that part of the said new or improved apparatus which
operates by means of a fusible metal are exhibted. Figures 19 and 20 represent an
apparatus intended to allow the escape of steam, to check or altogether destroy
the effect of the fire whenever the mass of water in the boiler becomes too
highly charged with heat, or whenever the level of the water sinks too near
the bottom of the boiler, but more particularly for the latter purpose; and this
apparatus is intended more particularly for hoilers containing a very little depth
of water over the bottom part of the boiler exposed to heat; c is bottom plate
of a boiler or generator; f is the lower end of a tube screwed into an inverted
cup g, which is screwed or riveted fast and water tight on the bottom plate of
the boiler through which the lower end of the said tube passes. Just above
the contracted part of the tube f (see Fig. 19), a plug of fusible metal is fixed
into a conical seat in the said tube f. The upper end of the tube f is connected
by a screw joint with a pipe h, descending through the top plate of the boiler
from a nossel or box (see Fig. 19), out of the upper part of which a passage i
proceeds horizontally, and then turns down at into the boiler. In the pipe or
passage, a cock m is placed for opening and shutting at will the communica-
tion between the passages h, i, and 1; n is a lever or handle for turning the
cock m. The handle n is secured in its position shewn in the Fig. 19, when the
cock on is open by a bolt or rod o, passing through the arms of a standard
such a manner that it cannot be drawn out without the padlock 7 being
previously unlocked. The upper end of the tube h is closed by a screw plug ";
and note, that a claw formed on the lever n catches over the top of the plug ";
as shewn at a, Fig. 19, so that the plug cannot be opened without unlocking.
the padlock 7. Now, as to the effect of this apparatus: if the body of water in
the boiler acquires too intense a heat, or if the water sinks below the level of
the top of the cup g, the heat of the water in the first case will be quickly
communicated to the metallic surfaces around the plug of fusible metal; and,
in the second case, the heat of the furnace will be quickly communicated
in

page_text: directly to the said lower end of the tube f, which I will call the conductor of
heat; and thus, in either case, such heat will be quickly communicated to the
plug of fusible metal, so as to melt the same and cause it to drop down into
the furnace, leaving an open passage through the tube f. Thus, the steam
proceeding from the boiler and which passes up through the tube 1, cock m,
passages i and h, and tube f will be allowed to issue into the furnace, and
damp or even extinguish the fire; for note, this apparatus should be placed just
over the fire grate. When the plug of fusible metal is melted, and the danger
having been prevented, the apparatus is to be put again in a condition to operate,
the emission of steam on the furnace must be cut off, unlocking the padlock,
withdrawing the retaining rod o, and shutting the cock m, which prevents the
fire from being completely extinguished, and allows of the tube f being cleaned
if necessary, and admits also of a fresh plug of fusible metal being introduced
as easily as if the boiler were not generating steam. For thus replacing the
plug the cap r must of course be removed, and a rod may if necessary be
introduced into the tube f, and used to drive home the metallic plug until it
be completely steam-tight; when this has been done, the cap will be screwed
on again in its place, and the cock m being turned round by its lever handle
into the position represented in Fig. 19, a passage will be again opened for
the steam to enter into the tube f. Note, the padlock 9 (which, it should be
observed, is to be kept locked constantly while the boiler is at work) puts it
out of the power of the stoker to stop the exit of steam (when there has been
a melting of the fusible metal), and to replace the metallic plug without giving
notice to the engineer who has charge in chief of the engine, and who should
keep the key of the said padlock. In Fig. 21, the pipe fis shewn fixed into
the bottom of the boiler itself, and projecting through it, so that the plug of
fusible metal will be affected by the heat, and melt even before the bottom of
the boiler or the body of water therein have acquired that sufficient tem-
perature at which the said fusible plug would melt. This may be desirable in
some cases. The operation of this construction of the apparatus, to let the
steam escape into the furnace and to cut off the escape of such steam for
replacing the plug, is exactly the same as that described in reference to the
Figures 19 and 20. Figures 22, 23, and 24, shew another mode of applying
fusible metal for the purpose of preventing the explosions arising from the
causes of explosion mentioned in reference to the Figures 19 and 20; and this
apparatus is adapted further to open a valve or a cock by means of the
melting of the fusible metal; fis the tube containing the fusible metal, the
lower end of such tube being enlarged, and projecting down through the box g,
to form a conductor of heat. Note, for this apparatus I prefer using a single

page_text: fusible metal instead of an alloy of metals, because in this apparatus the
fusible metal is not changed at each operation; a rod h rests on the fusible
metal, and round the upper end of such rod a spiral spring i is coiled,
fastened to the head of the said rod, the lower end of the spring i, resting upon
the nut which screws the tube to the boiler plate. To the head of the rod h
is connected by a joint pin, an upright stem l, with a level edge at its upper
end on or against which applies the corresponding bevel edge of a horizontal
lever m, poised on a fixed centre pin at n in the standard o. The weight p
keeps the end of the lever m down upon the end of the upright stem, and
tends to compress the spring i, and the upright stem is kept so upright by a
catch 1.
Now when the heat of the conductor of heat or box g, or of both,
have attained that degree at which the fusible metal will melt, and the same
begins to melt, the rod h being no longer supported, will yield to the pressure of
the weight p, and descend the end of the lever m pushing the end of the rod
away from it while the end of the said lever m falls down in an arc of a circle,
and gets by the end of the upright stem, which quits the retaining catch r;
the opposite end of the lever m will thus be raised, and may (by means of
suitable intermediate rods or levers,) raise a valve or a cock to let out steam
from the boiler at the same time, that the end of the lever m drops down past
the end of the stem 1; the spring i being no longer compressed by the weight p
will fly up, and thus withdraw the lower end of the rod from the fusible metal
before the same has hardened again. In Fig 24, the fusible metal is shewn
in a tube f, descending through the bottom of the boiler for the same purpose
as is mentioned in speaking of Fig. 21. In Figures 25, 26, 27, 28, 29, 30,
I have represented two modes of constructing that part of the said new
or improved apparatus which consists of an improved float apparatus.
d, Figure 25, is a box in cast iron or gun metal fixed to the top of the boiler.
The lower part of this box has a conical cavity in it, and the boiler has in this
place an aperture equal to the base of the cone, see Fig. 25. At the top of
the said conical cavity a small aperture is made, communicating between the
said cavity and the chamber g. The chamber g is connected by a pipe h,
and another conducting pipe, not shewn in the Drawing, to the flues which
surround the boiler; i is a vertical rod of gun metal, the upper end of which
is hemispherical. It is ground to fit accurately to the apex of the conical
cavity (see Fig. 25), so as to prevent steam from passing from the boiler into
the chamber g, so long as the rod i is kept in contact with the upper end or
apex of the conical cavity. The lower part of the vertical rod i has a shoulder
formed on it, below which a screw is cut for the nut / to screw on. In the
upper end of the rod i is a small square hole for the purpose of introducing a

page_text: key to grind the upper end of the said rod i, when the cap or cover mis
removed; and this operation may take place while the engine is working.
And note the cap m has in its centre a vertical hole, which receives a rod 1,
surrounded by a spiral spring 2 (see Fig. 25). The object of the rod 1 is to
allow the stoker to ascertain whether the float operates properly or not, for if
the upper part of the rod 1 be depressed, it acts on the rod i, lowers it, and
opening a passage from the boiler into the chamber g, allows steam to escape.
The spring 2 brings the rod 1 back to its former position, when the pressure
has ceased. K, K, is a fixed support or bearing piece fixed inside the boiler,
and under the top of the same (see Fig. 26). The perpendicular arms of the
frame K (see Fig. 26), receive the steel screws p, p, which are made with
points at their ends to form very fine pivots, on which the cross head 7 of the
lever J is poised or centred; 7 is the said horizontal cross head of the lever J,
which carries at its opposite extremity the hollow floating ball L (see Figure A,
where this apparatus is represented as attached to a boiler). The cross head I
turns, as will be seen by the Drawing, Fig. 26, on the steel points of the screws
p, p. The rod i passes through the lever J (see Fig. 25), the hole through
which it passes being large enough, and the screw nut l so adjusted as to allow of
play in the joint, and the lever J is prevented from descending below a certain
point by a guide or stop r. The operation of this apparatus is as follows:-
When the boiler is being filled with water to its usual level the floater, which
is fastened at the end of the lever J (see Fig. A, is pushed up by the water
as its level rises with a force equal to the difference between the weight of
the said, float and that of the volume of the water which it displaces. By
this effect of the float rising at the end of the long lever J, the rod i is pressed
against the aperture in the bottom of the steam chamber g, so as to close
exactly that aperture. Note, the float should be placed in the middle of
the length of the boiler, where the level is the most constant, especially in
boilers used in steam boats, in which the oscillation of the boat will change
every instant the level at the extremities of the boiler. If, in this state, the
fire is lighted to generate steam in the boiler, the equilibrium of pressure
soon establishes itself in all the parts communicating with the interior of the
boiler, and if, during the production of steam, and its eduction by the steam
pipe to work the engine, the level of the water is properly kept up by feeding
the boiler, the float L, as well as the lever J, will remain in the same
position, and motionless, consequently no effect will be produced; but if, on the
contrary, by any reason whatever, the quantity of water delivered into the
boiler from the feeding pipe becomes less than that which is converted into
steam, the level of the water, by sinking progressively, would soon reach the

page_text: level of the upper part of the flues, and thus expose the side of the boiler
unprotected to the heat of the flame and hot air in the flues. This however
will be prevented by the action of the float L, which, sinking down gradually
with the water, will draw down the rod i in opposition to the resistance
which the steam exercises on the surface of the rod to retain it against
the small aperture in the bottom of the chamber g, which it generally closes.
When this effect is produced, (and it should be produced when the water is
still considerably above the line of the upper part of the flues), the steain
will escape from the boiler through the little aperture opened by the drawing
down of the rod i, and will pass into the steam chamber g, and thence through
the pipe h, away either to the flues to check the draft, as herein-before
mentioned in speaking of other parts of the apparatus, or else into or under
the furnace, or else into the atmosphere.
It
In Figures 27, 28, 29, 30, the second mode of constructing the said im
proved float apparatus is shewn. a is the upper part of a boiler, represented
in a longitudinal section; b is a tube, screwed with a steam-tight joint through
the upper plate of the boiler.
grows out at the upper part into a box or
steam chamber, and out of which a horizontal pipe h leads, and the lower
end of the said tube b is formed of a hemispherical shape, the curve of which
forms a sharp angle, with the aperture of the tube b. The steam chamber c
is closed by a screw cap e. A small horizontal pipe f leads out of the tube b,
below the steam chamber c, and in the bottom of the chamber c is a conical seat,
into which is ground a valve consisting of a small tube g, in which is placed
a spiral spring kept pressed down by a stud projecting down from the cap e;
and note, the the tube g must be made to, rise very freely. K, K, are the
bearers for carrying the screw centres p of the lever J, which differs from
the lever J in the preceding description only in having a hemispherical plug
or valve a of lead or tin to apply against the aperture of the tube b, instead of
a rod i; the said plug or valve a is soldered into the head of a screw bolt y,
as in Fig. 25, which is secured by a nut (see Fig. 27); the plug or valve a
applying as aforesaid against the mouth of the pipe b, forms as it were a
self-adjusting fitting therewith, for the force with which the float L is raised,
by reason of its buoyancy, will cause the soft metal of the plug or valve to
be slightly indented by the sharp edges of the tube b, and thus a perfect contact
will be effected. At the extremity of the lever J is fixed the float L, which
is a hollow ball of copper (see Fig. A). A tube m is soldered to the float
L (see Figures 27 and A). This tube is open at its upper end and communi-
cates to the float I. at the other end to admit freely the steam and air to pass

page_text: through the pipe m into the float, for the purpose of preventing the said
float from having its sides crushed in by the external pressure of the steam
upon it, or from bursting by the expansion of the air within it produced by
the heat of the steam. The operation of this construction of the float
apparatus is the same as that of the preceding one, so far as regards its
effect in closing the aperture by which the steam is to escape when the level
of the water sinks too low, except that from the application of the soft metal
plug or valve. To effect such closing of the said aperture a better and more
certain fitting will be obtained, and there will be less liability of any sticking
fast of the surfaces, and, so long as the proper level is maintained, all the parts
will be in perfect contact, so that the steam will not escape; but if, while steam
is being generated in a boiler, it happens from any accidental cause that a
proper supply of water is not kept up, the level will sink progressively until
it approaches the distance from the upper parts of the flues beyond which
it ought not to descend. If the water continues to get lower the float L will
sink with the water and open the outlet for the steam, which will escape at
first in a small quantity by the pipe f, and will gradually increase in quantity
as the level of the water in the boiler sinks more and more. The steam
which thus escapes is conducted by the said pipe f out in front of the boiler,
where the stokers is placed, to give him notice of the sinking of the level of the
water below the proper line. If, notwithstanding the notice so given, the stoker
allows the level to continue sinking, the opening for the escape of the steam
encreasing, a greater quantity of the steam will require to escape than the
pipe fis calculated to give passage to; the steam, therefore, accumulating under
the valve g will lift it up, in spite of the resistance of the spring herein-before
mentioned, and rush out by the larger pipe h, and so into the flues or furnace,
or into the ash pit, to check or wholly destroy the effect of the fire; or instead,
such steam may be conveyed to any part of the building if it be a stationary
boiler that the apparatus is applied to, or of the vessel if it be a marine
engine, to act upon a pipe made like an organ pipe, or upon a bell, to give
notice to the chief engineer of the danger. As the effect of the apparatus is
to prevent any overheating of the suface of the boiler, a fresh supply of water
may be immediately introduced, and as the water is regaining its proper level
the float will rise with it, and bring the hemispherical valve of soft metal
against the aperture of the tube (6), and close it as before, so as to prevent
completely any further escape of steam. The aperture of the tube b, for the
escape of the steam, is of a very small dimension compared with the capacity
of the boiler. This is to prevent, as aforesaid, the escape of the steam from

page_text: being too great and instantaneous, which might excite a great and unusual
ebullition of the water, and it is quite sufficient if the escape of steam checks
the effects of the furnace or gives notice as aforesaid.
In Figs. 33 to 36 I have represented one mode. of constructing that part
of the said apparatus which consists of dampers applied on the flue of steam
boilers to act by the motion of the boat inclining the boiler to one side or the
other. Fig. 38 is a cross section of a boiler and furnace with the said dampers.
Fig. 34 is a side view. of one end thereof. Fig. 35 shews the dampers viewed
edgewise in cases formed for them to work in; and Fig. 36 shews one of the
dampers detached viewed edgewise. Note, in the Drawing the boiler is shewn
as set in brick, which is not usual in steamboat boilers; this is merely done
to shew the flues more easily. C, C, are the side flues; E, is a cast-iron
case let into each side of the flue to receive one of the 'dampers; F is a door
closing such case; G, G, are the dampers, hanging freely from pivots' or
centre pins H, let into the cases E. The apparatus, as before mentioned, is
particularly adapted for marine boilers to act by the inclination of the boiler
when the boat lies over on its side, and the effect of the said suspended
dampers is as follows:-So long as the steam vessel containing the apparatus
remains upright, the dampers G, (which, by their gravity, tend to maintain
a vertical position) will be in respect of the flue in the positions shewn by
the Drawings, that is not interrupting the current of heated air and flame in
the flues, but if the said steam vessel; in tacking or otherwise, is laid over
on its side for any length of time the boiler will of course incline over also
to one side, whereby 'the opposite side of the boiler would be left bare of
water, and exposed to become too much heated, and then the passage through
the flue on the exposed side will become partially or wholly closed by the
damper G belonging to it, because the flue C will rise upwards and move
towards the daniper G, while the said damper remains vertical, (see the
Figure 33, by inspection of which the operation of the suspended dampers
will be easily understood,) and hence the draft on the side of the boiler
exposed to danger will be checked or stopped altogether. Note, the
rotatory motion of the axis of suspension of the dampers may be communi-
cated by suitable mechanism, if it be desired, to a valve to lift the same and
llow stea i to escape from the boiler and "enter the flue in which it is
desired to check the draft and drive the current of heated air and flame back
towards the furnace. Instead of constructing the apparatus as above des-
cribed, the dampers may be made and placed to have the effect of sliding
dampers (although they will not themselves move), by connecting them by
suitable connecting rods (and other intermediate mechanism, if requisite)
B

page_text: with heavy or loaded rods, suspended so as to hang freely from axes, which
may be fixed to the boiler, or to some convenient part of the roof of the
engine room, so that when the vessel inclines over to one side, the said sus-
pended rods. remaining vertical by their own gravity, the dampers which are
connected to them will remain stationary, notwithstanding the inclination of
the vessel; and hence, that side of the boiler which rises will advance or rise
towards its damper, and the passage through such flue will be wholly or partially
cut off or closed, according to the extent of the motion of the vessel, while
the opposite flue will, on the contrary, recede from its damper; or the same
effect, may be, produced, either in the flues, or in the chimney, by applying
within each of the flues, or in the chimney, a. damper throngh which passes
an, axis. resting in, necks formed in the sides of the flue or of the chimney,
such damper being placed so as to have the plane of its surface parallel to
the sides of the flue or chimney in one position, but so as that by turning its
axis a half turn the plane of its surface will lie across the passage, or at
right angles to the sides of the flue or chimney, in the manner of the throttle
valve of a steam engine. On one end of the axis of such damper a short
crank will be formed, which will be connected by a connecting rod to the
lower end of a loaded rod suspended from an axis fixed to some part of the
boiler or of the vessel, so that when the boiler or chimney is inclined over to
one side by the inclination of the vessel, the crank on the axis of the damper
being restrained by the said loaded lever (which will not as aforesaid depart
from verticality), the effect will be to turn the axis of the damper round more
or less, according to the degree of inclination of the part to which it is
attached, and according to the proportion between the length of the crank
on the axis of the damper, and the length of the point where the connecting
rod is jointed to the loaded rod from the centre of suspension of such rod;
and note, that in the several modes of constructing the said apparatus above
mentioned, it is essential that the axis of the dampers when they are them-
selves suspended, or of the heavy rods when such are used to act with
the dampers, should be fixed to such parts of the boiler or vessel as partake of
or are affected by the inclination of, the vessel, while the lower ends of the
suspended dampers or of the suspended rods should, on the contrary, be as
near as possible to the centre of oscillation or point of repose of the vessel. I
have not, thought it necessary to, describe further the varieties which may
occur in the modes of applying dampers. to be acted upon by the inclination
given by a steam boat to its boiler, as they will depend on the nature and
form of each particular variety of boiler to which the same may be applied
and on considerations, of: local conveniencies, and will be readily made, by a

page_text: competent engineer, the peculiarity of this part of the said new or improved
apparatus consisting wholly in causing dampers in the flues or chimneys' of a
marine boiler to produce their effect by either suspending such dampers
themselves, or connecting them with other heavy suspended bodies, so that the
motion given to the boiler itself combines with the resistance to departure
from verticality of such dampers or heavy bodies with which they are con-
nected, to produce the effect of sucli dampers closing the passages. in which
they are to operate. I have herein-before stated that all the parts of the said
new or improved apparatus may be applied in combination or separately. It
must of course be matter of discretion with the engineer fitting up a steani
boiler when to do the one and when the other. The part last described is, as
I have stated, only applicable properly to steam boat boilers, such boilers only
being exposed to the dangers arising from their licing inclined over to one side,
so as to make the level of the water sink on the opposite side. . The appa-
ratus described in reference to Figs. 7 to 14 will probably be found necessary
chiefly, if not, only, where the water forms a deposit or incrustation in the
bottom of the boiler; and for stationary boilers, working under favorable
circumstances, only the compound safety valve, the float apparatus, and
the apparatus Figs. 15 to 18, may be required. As to the proportions and
arrangements of the various parts, and the metals of which the same are
to. be composed, the selection thercof must be matter of discretion for the
engineer constructing the apparatus, except that I will observe, that I make
usually the parts destined to transmit heat of gun metal. I will, however, also
observe, that in respect to all the apparatus acting by means of fusible metal,
the apertures through which the steam is allowed to escape are to be made of
such size as not to allow the steamr to escape suddenly in great quantities.
Having now described the nature of the said Invention of a new or
improved apparatus for preventing the explosions of boilers or generators of
steam, I hereby declare that in respect to the part of the said new or improved
apparatus firstly described, I claim the combination which I have described, of
a common safety valve, with a piston or plunger operating in a cylinder filled
with oil or other fluid, on which the steam is allowed to act, such combination
beng effected in such manner that when the said common safety valve is in
proper order, it can act and rise to a certain point: independently of the
plunger; but so. that, whenever the said. common safety valve sticks fast in its
scat from any cause, or when it is raised too violently, the piston or plunger
is brought into operation, in the first case to help it by the pressure of the
steam on the fluid raising the said piston or plunger,, and. in: the second case,
to check and regulate its motion as hererein-before described. And as to
those parts of the said new or improved apparatus, in which a fusible metal is.

page_text: applied, I do not claim generally the application of a fusible metal to be
acted upon by the heat applied to steam boilers; but I claim that combination
of pipes, cocks, steam boxes or chambers, and other parts which I have
described, by the effect of which the heat of the steam alone, or of the steam
and water and heated-surfaces near or within which the fusible metal is placed,
is admitted to act upon such fusible metal, and to open, by melting it, a passage
for the superabundant steam to escape, the parts aforesaid being so combined
also that the apparatus may operate as I have described, and be replaced after-
wards in a state to operate again without necessarily stopping the engine. And
in respect to that part of the said new or improved apparatus which consists
of an improved float apparatus;. I claim only that combination of parts which
I have described in reference to Figs. 25 to 30, on the sheet, of Drawings
hereunto annexed. And, lastly; I claim an apparatns composed of dampers
suspended themselves or connected with and restrained by other suspended
heavy or loaded bodies, the effect of such dampers to close partially or wholly
the flues or chimney of a steam boat boiler being produced by applying the
motion of the vessel itself when it inclines over to one side, in combination
with the resistance to departure from verticality of the suspended dampers, or
of the heavy bodies with which they are connected, as I have herein-before
described.
In witness whereof, 1, the said Charles Pierre Devaux, have hereunto
set my hand and seal, this Twenty-third day of November, in the
year of our Lord One thousand eight hundred and thirty-seven.