Year: 1887

page_text: Date of Application, 7th May, 1887
Complete Left, 8th Feb., 1888
Complete Accepted, 9th Mar., 1888
1, EVAN HENRY PARRY, of 8 Fisher Street, Swansea in the County of Glamorgan,
Engineer do hereby declare the nature of this invention to be as follows:-
:-
My invention relates to fusible safety plugs for steam boiler farnace tubes and
consists in an improved arrangement or construction of said plugs, the object of my
improvements being to protect the fusible metal from the chemical action of the
water in the boiler and of the gases in the furnace.
The body of my improved safety plug consists of a short brass tube turned and
smoothly finished all over and screwed at the lower end to fit into a correspondingly
tapped hole in the furnace tube crown. At the upper part the body is formed with
a valve seating for the support of the cap. The latter consists of an inner conical plug
or cup and an outer conical ring or shell, both of brass, with a space between them.
The said outer ring or shell is formed at its narrower end with a circular rim or lip
projecting inwardly so that the internal diameter of the opening inside the rim is
slightly smaller than the outside diameter of the conical plug at its smaller end and the
rim overlaps this end of the plug. Both parts are turned and fitted together by
grinding so that the rim forms a flat or conical perfectly water tight valve seating for
the plug. Circular grooves or threads may be cut on the outer surface of the plug
and the inner surface of the ring. The two parts are held together fitting tight upon
cach other at the watertight seating, while molten white metal alloy of the desired
fusing temperature is poured into the annular space between them, which alloy after
cooling holds the two parts together and forms with them a solid cap. The larger end
of this cap is then turned and ground to fit watertight on the valve seating on the top
of the body herein first described, and is held in its position by a cotter passed over
the top of the cap through lugs cast upon the body or seating tube. The inside
diameter of the valve seating is one sixteenth to one eighth of an inch larger than the
largest outside diameter of the conical plug, so that the cap rests upon the seating
partly with its outer ring and partly with the fusible alloy and the inner plug can
drop through the valve seating when the metal alloy becomes fused through excess of
temperature.

page_text: By arranging the cap and body of the safety plug as described, the fusible metal
alloy is protected by the watertight lip of the ring from contact with the water in the
boiler, which if strongly alcalino rapidly corrodes or destroys such alloys and alters
their composition and fusing temperature, and by resting on the seating the fusible
alloy is also protected from the action of the combustion gases in the furnace, while
the conical plug is so held that it easily passes through the seating when released by
the fusion of the metal alloy.

page_text: I, EVAN HENRY PARRY of 8 Fisher Street Swansea in the County of Glamorgan
Engineer 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 :-
My invention relates to fusible safety plugs for steam boiler furnace tubes and
consists in an improved arrangement or construction of said plugs, the object of my
improvements being to protect the fusible metal from the chemical action of the water
in the boiler and of the gases in the furnace.
On the sheet of drawings appended hereunto,
Fig. 1 shows a vertical section of my improved fusible plug.
Fig. 2 a vertical section at right angles to the former with cap removed.
Fig. 3 shews a horizontal section along line W. X.
And fig. 4, a horizontal section along line Y, Z, on fig. 1.
b
The body a of my improved safety plug consists of a short brass tube turned and
smoothly finished all over and screwed at the lower extremity a¹ to fit into a corre-
spondingly tapped hole in the furnace tube crown. At the upper part it is formed
with a valve seating a for the support of the cup. The cup consists of an inner
conical plug or cup 6 and an outer conical shell or ring c, both of brass, with a space
between them. The outer ring or shell c is formed at its narrower end with a circular
lip or flange c' projecting inwardly so that the internal diameter of the lip is slightly
smaller than the outside diameter of the conical plug b at its smaller end. By
preference the plug 6 is recessed slightly for the lip c¹ as shown but the latter may
also simply overlap the top of plug b. Both parts are turned and ground or accurately
fitted together so as to form a perfectly water-tight joint. The lip c¹ may also be bored.
conically and fitted upon the sides of the conical plug b at the top, the essential point
of my invention being a projecting lip forming a water-tight joint against the internal
plug and thereby protecting the fusible alloy against the action of the water, which
especially if strongly alkaline rapidly corrodes or destroys such alloys or alters their
fusing temperature.
Circular grooves, as shewn, or threads may be cut on the outer surface of the
plug b and the inner surface of the ring c. The two parts are held fitting tight
together upon each other at the watertight joint while molten white metal alloy e of
the desired fusing temperature is poured into the annular space between them, which
alloy after cooling holds the two parts together and forms with them a solid cup. The
larger end of this cup is then turned and ground to fit watertight upon the valve
seating and is held in its position by a cotter d passed over the top of the cup
through lugs a a' cast upon the seating tube or body a. The inside diameter of the
valve seating a² is a little larger than the outside diameter of the conical plug b, so
that the cup rests upon the seating partly with the fusible alloy e and partly with the
shell c and the plug b can drop through the seating a³ when the alloy e becomes fused

page_text: through excess of temperature. By preference the lower end of the plug projects
slightly below the bottom edge of the conical seating and the alloy surrounding this
is turned cylindrically so as to fit into the bore of the seating a and thereby secure
the cup in its correct position upon the conical seating a². By resting upon the latter
the alloy e is protected against the chemical action of the combustion gases upon it.
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,
Firstly, the arrangement or construction of fusible plugs for boiler furnace tubes
substantially as herein before described and shewn on the drawings.
Secondly, forming the outer shells of the cups with internal lips or flanges at the
top bearing upon or against the internal plugs substantially as described and for the
purpose set forth.
Thirdly, arranging the cups of fusible plugs so that the fusible alloy rests upon
the seating for the cup, substantially as described and for the purpose set forth.
בד
J
Wah 1000
EMMOTT & Co.,
Agents for the Applicant.