IMPROVEMENTS IN FUSIBLE PLUGS FOR STEAM GENERATORS AND OTHER APPARATUS
Year: 1877

page_text: LETTERS PATENT to Henry Hiller, Chief Engineer of the National Boiler
Insurance Company, of Manchester, in the County of Lancaster, for the Inven-
tion of "IMPROVEMENTS IN FUSIBLE PLUGS FOR STEAM GENERATORS AND OTHER
APPARATUS."
Sealed the 1st June 1877, and dated the 19th February 1877.
PROVISIONAL SPECIFICATION left by the said Henry Hiller at the Office
of the Commissioners of Patents on the 19th February 1877.
HENRY HILLER, Chief Engineer of the National Boiler Insurance Company, of
Manchester, in the County of Lancaster. IMPROVEMENTS IN FUSIBLE PLUGS FOR
"
STEAM GENERATORS AND OTHER APPARATUS."
My Invention relates to the appliances which are now well known as Smith's
fusible plugs, and to plugs constructed on a similar principle. In the said plugs an
inner cone is secured within an outer cone by means of an interposing stratum of
fusible metal which has hitherto been run in a melted state into the space between
the two cones.
When the said fusible metal has been melted and the inner cone
has thereby been released, it has been necessary to renew both cones, or to remove
both cones for repairs.
The principal object of the first part of my Invention is to remedy this defect,
and in some cases to enable the said inner cone to be fixed within the outer cone
whilst the latter is in position without entering the steam space of the boiler, and
this I accomplish by so forming the parts that the inner cone with a coating or
envelope of fusible metal can be secured within the outer cone without removing
the latter from its place in the steam generator. This I accomplish by forming the
said fusible coating to screw into threads formed within the outer cone, or by so
constructing the inner cone as that the envelope of fusible metal can be expanded
so as to be forced to engage with grooves, threads, or recesses formed in the interior
of the outer cone, or to become attached to the roughened surface of the said
interior. The screw thread or threads on the fusible metal may be formed in the
casting operation, or by cutting or chasing, and may be of a square or vee-shape,
or of any suitable form. The said screw threads may be formed on the conical
surface or on a cylindrical part formed at the base of the inner cone and the
said cone may be formed with a socket of hexagonal or other form to receive a key,
5 Dine C71

page_text: or with a projecting shank suitably formed to engage with a key, and serving also
as a heat conductor. To prevent the inner cone turning within the envelope of
fusible metal, I prefer to form flat sides or recesses on the said cone.
When constructing the inner cone to expand I employ a split cone, and I expand
the said cone when in position by means of a conically formed pin or key which is
arranged to be driven or screwed into an orifice in the said cone, and thereby to
expand the same or by screwing or forcing the said cone into the envelope of fusible
metal. The said outer cone or a shell corresponding thereto may be formed to
receive more than one inner cone or plug.
A second part of my Invention consists in forming a flanch on the base of the
inner cone, the said flanch, being formed of the harder metal of the said cone and
projecting over the base of the fusible metal. When the said inner cone is fixed in
position the said flanch prevents the direct action of the fire upon the fusible metal,
and also prevents the running out of part of the fusible metal before the whole is
sufficiently melted to permit the inner cone to be blown out.
A remaining part of my Invention consists in forming a short outer cone with a
flanch which is turned to a valve-shaped form, the bush which is screwed into the
boiler or fire-box shell being turned to correspond. The said cone is placed on the
top of the said bush, and is secured thereto by means of a cap arranged to screw
upon the said bush, or is passed into the bush and fixed by means of a thimble
arranged to screw into the bush. In this part of my Invention the inner cone may
be fixed in the ordinary manner, or by the means indicated when describing the
first part of my Invention.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Henry Hiller in the Great Seal Patent Office on the 10th August
1877.
"
HENRY HILLER, Chief Engineer of the National Boiler Insurance Company, of
Manchester, in the County of Lancaster. IMPROVEMENTS IN FUSIBLE PLUGS
FOR STEAM GENERATORS AND OTHER APPARATUS."
My Invention relates to the appliances which are now well known as Smith's
double cone fusible plugs, and to plugs constructed on a similar principle, and
employed to prevent damage to steam generators arising from deficiency of water
as is now well understood. In the said plugs an inner cone is secured within an
outer cone by means of an interposing stratum of fusible metal which has hitherto
been run in a melted state into the space between the two cones. When the said
fusible metal has been melted and the inner cone has thereby been released, it has
been necessary to renew both cones, or to remove both cones for repairs.
The principal object of the first part of my Invention is to remedy this defect,
and in some cases to enable the said inner cone to be fixed within the outer cone
whilst the latter is in position without entering the steam and water space of the
boiler; and this I accomplish by so forming the parts as that the inner cone with a
coating or envelope of fusible inetal can be secured within the outer cone without
removing the latter from its place in the steam generator. This I accomplish by
forming the said fusible coating to screw into threads formed within the outer cone,
or by so constructing the inner cone as that the envelope of fusible metal can be
expanded so as to be forced to engage with grooves, threads, or recesses formed in
the interior of the outer cone, or to become attached to the roughened surface of the
said interior.
A second part of my Invention consists in forming a flanch on the base of the
inner cone, the said flanch being formed of the harder metal of the said cone and
projecting over the base of the fusible metal.
A remaining part of my Invention consists in forming a short outer cone with a
flanch which is turned to a valve-shaped form, the bush which is screwed into the

page_text: boiler or fire-box shell being turned to correspond. The said cone is placed on the
top of the said bush, and is secured thereto by means of a cap arranged to screw
upon the said bush, or is passed into the bush and fixed therein by means of a
thimble arranged to screw into the bush..
And in order that my Invention may be more readily described and understood, I
have appended hereunto a Sheet of Drawings made about the full size, and marked
with letters of reference, to which Drawings I will now refer.
Fig. 1 represents a vertical section of a complete fusible plug constructed in
accordance with the first and second parts of my Invention; and Fig. 2 is a plan of
the plug reversed to shew the interior. In the said Figures, A is the said outer.
cone which is suitably formed to screw into the furnace crown or part to which the
plug is to be affixed, represented by b. The upper part c of the said outer cone is
bored or formed to a conical shape, and at the base of this cone is formed a
cylindrical part d which is chased or tapped, or is otherwise formed with a screw
thread. The inner cone Ę is made partly conical and partly cylindrical in form.
The conical part is turned to a true conical form or is left rough, or is cast or formed
with recesses or with flat sides, as considered to be most suitable. I prefer to form
a screw thread on the cylindrical part of the said inner cone, and when so formed
the conical part may be turned and need not be formed with recesses or means
for securing the envelope of fusible metal other than the said screw thread. I also
prefer to taper the thickness of the envelope, but do not confine myself to this
formation. The base of the said inner cone is formed with a flanche which is a
little larger in diameter than the bore of the cylindrical part d The envelope of
fusible metal is represented by the solid black lines between the parts A and E.
This envelope is cast upon the inner cone E, and is subsequently turned and screwed
or chased to fit and screw into the outer cone A, or it may be found to be con-
venient to cast the envelope of fusible metal upon the said inner cone in a mould
which would be constructed to impart the required form to the outside of the said
envelope, and to form the screw thread upon the cylindrical part; thus dispensing
with the necessity for turning the fusible metal to fit the inside of the outer cone;
or the envelope may be cast or formed separately and be subsequently screwed
upon the inner cone, in which case the said inner cone would be formed with a
screw thread, as herein-before mentioned, and as indicated in the Drawing. It is
necessary that the outer surface of the said envelope shall fit the interior of the
cone c with an amount of exactness sufficient to prevent the escape of water when
the inner cone is screwed into its place within the outer cone. When so screwed
into position the flanch e covers the base of the envelope of fusible metal, and
prevents the direct action of the fire upon the said metal.
In the case of ordinary plugs the fusible metal sometimes melts partially so as to
permit a slight escape of steam which arrests the fusion of the plug, and thereby
prevents a sufficient and free outlet for the escape of steam from being secured.
The flanch e is intended to prevent any portion of the fusible metal from running
out until the whole of it is fused sufficiently to permit the inner cone to be blown
out, the indicated defect in the ordinary plugs being thus remedied.
The arrangements for screwing the inner cone E into position may be varied. In
the example the said inner cone is formed with an internal cavity, a part of which
cavity is of an octagonal form, as seen in Fig. 2. A key represented by Fig. 3 is
formed to fit into the octogonal part of the said cavity.
When an inner cone has to be inserted into the outer cone A it is simply
necessary to place the said inner cone on the key to insert it into the part A and to
screw it into position by turning the key. When an inner cone has been blown
out a fresh inner cone can be screwed into position without emptying the boiler, it
being only necessary under ordinary circumstances to "draw the fire" and to cool
the furnace sufficiently to enable an operator to get the inner cone into position, a
comparatively short delay being occasioned. The cavity in the inner cone may be
made of a square, hexagonal, or other form, or slots may be cut or formed in the
base, as in the case of an example to be described herein-after, the key being formed

page_text: to correspond; or the said inner cone may be formed with a shank on to which the
key will be arranged to fit as preferred.
The form and proportions of the inner cone and of the cavity in which it is fixed,
and the form and arrangement of the screw thread may be varied.
Fig. 4 illustrates a modification in the forms of the said parts, and represents the
inner cone as being formed with a shank projecting into or towards the fire-box.
The end of the said shank is squared or is otherwise formed to be turned by means
of an ordinary or a special key, as preferred, in order that the inner cone may be
screwed into position.
Fig. 5 is a vertical section of a plug which is fitted with an expanding inner
cone. In this example the inner conical surface of the part A is formed with
grooves. The inner cone E is formed with a central conical hole, and is split at one,
two, or more places around the said central hole, the split, or each split extending
nearly throughout the depth of the cone, as indicated by the dotted lines. The
outer surface of the said inner cone is formed with recesses to hold the fusible metal.
The envelope of fusible metal is supposed to be cast upon the said inner cone, and
is turned or formed to fit the inner conical surface of the part A. A conical pin f
is formed to enter the central hole in the said inner cone. To fix the inner cone
with its envelope of fusible metal in position, the said cone is passed into position
within the outer cone A, and the pin f is driven into the inner cone so as to expand
it, and thereby to force the fusible metal into the grooves in the outer cone. I do
not now consider this method to be so suitable as the method of fixing by screwing
the inner cone into the outer cone.
If preferred the said conical pin may be formed to be screwed into the split cone
instead of to be driven therein. The inner cone is formed with a flanche in
accordance with the second part of my Invention. The remaining Figures illustrate
the third part of my Invention.
Fig. 6 is a vertical section; and Fig. 7, a plan of a fusible plug. In this example
the outer cone A is changeable, and is provided with an inner cone E which may be
fixed in position in the usual manner by pouring the melted fusible metal into the
space between the two cones. The lower part of the cone A is formed with a flanch
which is turned with a conical surface to fit the end of a bush G which is arranged
to screw into the shell of the fire-box or into the part to which the plug is to be
applied, the part A fitting the part G in manner similar to the fitting of a valve
upon its seating. The bush G is chased or screwed to engage with a nut h which
is formed with an inner flanch which bears upon the flanch on the cone A. The
said nut is formed with flat sides, or is otherwise formed to be turned by means of
a key. When the inner cone of a plug has been melted out the outer cone A is
removed by unscrewing the nut h, and a fresh cone is put in the place of the one
removed; the nut is then passed over the cone into position, and is screwed down
tight so as to secure the cone to the bush G in a fluid-tight manner. The inner
cone E is formed with a flanch e as in the previous examples.
Fig. 8 illustrates a modification in the example last described, the said Figure repre-
senting a vertical section of a complete plug. In this example the cone A is shorter
than in Fig. 6, and is formed with a flanch which is turned to fit tightly against an
inner projecting flanch which is formed on a shell i, which is formed to screw into
the crown of the fire-box, or to the part to which the plug is to be applied. A screw
thread is formed in the interior of the shell i, and a nut or thimble k of an annular
form is screwed or chased to suit the said screw thread. In the example, four slots
are cut or formed in one edge of the said nut, and a key is formed with projections
to enter the said slots, as indicated by Fig. 9, which represents an end view of the
said key. The said key is formed with a suitable handle. The formation of this
plug enables the cone to be replaced without entering the steam and water space of
the boiler. In the event of the inner cone E being melted out the outer cone A is
removed by unscrewing the nut / by means of the key, and a fresh cone containing
an inner cone attached by fusible metal, as in the case of Fig. 6, is passed through
the shell into position; the nut k is then introduced and screwed up tight by

page_text: means of the key so as to form a tight joint between the flanch on the cone A and
the inward projecting flanch on the shell i, the change being effected when the
furnace or fire-box can be entered, as in the case of the plugs described under the
first head of my Invention.
I do not confine myself to the form of key employed, nor to the number of slots
or holes cut or formed in the nut k, as these may be varied as considered to be most
suitable.
Having now fully set forth and indicated the nature of my said Invention, and
methods whereby the same may be carried into practical effect, I would have
it to be understood in conclusion that I claim,-
First. The appliances, substantially as and for the purposes set forth and indicated
herein-before and in and by the accompanying Drawings.
Secondly. Forming or providing the inner cones of "plugs" with envelopes of
fusible metal which are formed to screw into the interiors of the outer cones, sub-
stantially as set forth and indicated.
Thirdly. Forming the inner cones of "plugs" to be expanded so as to force the
envelopes of fusible metal to take hold of the prepared interiors of the outer cones,
substantially as set forth and indicated.
Fourthly. The flanch e, substantially as and for the purpose set forth and
indicated.
Fifthly. The fusible plug formed and fitted, substantially as set forth and indi-
cated herein-before, and by Figs. 6 and 7 of the accompanying Drawings.
And, Lastly. The fusible plug formed and fitted, substantially as set forth and
indicated herein-before, and by Fig. 8 of the accompanying Drawings.
In witness whereof, I, the said Henry Hiller, have hereunto set my hand and
seal, this Second day of August, in the year of our Lord One thousand eight
hundred and seventy-seven.
Signed and sealed by the
said Henry Hiller in
the presence of
EDWARD K. DUTTON,
Agent to the Patentee,
3, Princess Street,
Manchester.
4
HENRY HILLER. (L.S.)