Improvements in and in the Manufacture of Safety Plugs for Steam Generators.
Year: 1893

page_text: Date of Application, 8th Aug., 1893-Accepted, 9th Sept., 1893
COME LEID DIBUITRATION.
Improvements in and in the Manufacture of Safety Plugs for
Steam Generators.
I EDWARD GEORGE HILLER, Chief Engineer and Manager of the National
Boiler and General Insurance Company Limited of 22 St. Ann's Square,
Manchester in the County of Lancaster 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 and accompanying
drawings:-
My invention relates to the safety or fusible plugs which are intended to provide
outlets for the escape of steam from steam generators in the event of the water
level becoming lowered to a dangerous extent as is well understood and is applicable
to plugs of the general formation illustrated in the drawings attached to the
Specification of an invention for which Letters Patent number 3565 of the
year 1888 have been granted to Henry Hiller and to other plugs having outer
and inner cones. In such plugs as made by or for my Company a fusible alloy
has filled the space between an outer and an inner part of conical formation and
a flange upon the larger end of the inner cone has shielded the fusible alloy from
the direct action of the fire. According to my invention I also provide a flange
or projecting lip or ring at the upper end of the combination to shield the fusible
alloy from the water.
My invention will be best understood when described with reference to the
accompanying drawings of which
Fig. 1 represents a vertical section through the centre of my improved plug,
Fig. 2 being a plan view of the plug.
In the said figs. a is the outer cone 6 is the inner cone and c is the fusible alloy.
The aforesaid flange upon the inner cone is shown at 6. The inner cone is smaller
than the interior of the outer cone so that there is a space all round the inner
cone to contain the fusible alloy as in the ordinary construction.
Previously to my invention the fusible alloy has extended upward entirely
through to the upper surface so that the water in the steam generator has had
free access to the exposed surface of the fusible metal. To prevent such access I
provide a projecting lip or ring a' which extends inward from the interior of the
cone a and touches or nearly touches the upper end of the inner cone 6 and shields
the fusible metal. This lip may be of any suitable form but I prefer that it shall
have a sharp or thin edge as shown in the drawing. If preferred the lip or ring
might be formed upon the inner cone, or the lip on the outer cone might extend
a little over the upper end of the inner cone so as more effectually to shield the
fusible alloy but at present I consider the amount of protection indicated to be
sufficient. It will be apparent that the space between the two cones is closed at
both ends when the inner cone is in position and it will not be possible to fill the
space in the ordinary manner. I adopt special means to overcome this difficulty.
I either fill or partly fill the outer cone with fusible metal and then force the
cone 6 into place or I fill the space with the larger end of the cone 6 projecting a
little from the space and then force the cone home. I find it convenient to immerse
the outer cone a in the melted fusible metal or to immerse both cones with the
inner cone projecting and then to press home the inner cone so as to force out the
superfluous alloy.
b
It will be seen that when the inner cone has been pressed nearly home there
will be a restricted outlet for the escape of the fusible alloy so that the latter
will be subjected to compression. I consider this to be an advantage for the
reason that the alloy is forced into all parts of the space so as to entirely fill the

page_text: same and is brought into close contact with the metal of the cones so that trans-
mission of heat from one to the other will be more effectual than would be the
case with an imperfectly filled appliance.
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 1
claim is.
1. The combination of inner and outer cones and fusible alloy as and for the
purpose set forth and illustrated.
2. The lip a' on the cone a as and for the purpose set forth and indicated.
3. In so termed fusible plugs for steam generators forming the upper end of the
outer or inner cone with a projecting lip or ring to shield the fusible alloy from
the action of the water substantially as set forth.
4. The method or methods of filling the spaces in fusible plugs with fusible
alloy including the application of pressure to the inner cone to expel the superfluous
alloy as set forth.
Dated this 5th day of Aug 1902
E. K. DUTTON & Co.,
5, John Dalton Street, Manchester, Agents.