Improvements in or applicable to Low Water Safety Valves for Steam Boilers.
Year: 1896

page_text: Date of Application, 12th Sept., 1896
PROVISIONAL SPECIFICATION.
Improvements in or applicable to Low Water Safety Valves for Steam
Boilers.
We, JAMES ASHTON FLETCHER and SAMUEL FLETCHER, both of Borough Brass
Works, Ashton-under-Lyne, Brass Founders, do hereby declare the nature of this
invention to be as follows:-
Our said invention relates to improvements in or applicable to low water safety
valves that is to say valves which automatically open and permit the escape of steam
in the event of the water level sinking too low.
One part of our said invention relates to the floats used in combination with such
valves.
According to our said invention the float consists of a number of hermetically
sealed tubes assembled together so as to form a kind of raft or float which while
possessing greater buoyancy than the present floats will not be so liable to
destruction. In some cases we seal up water or liquid in the tubes of the float
which on vapourising under the action of the surrounding heat will produce an
internal pressure in the interior of the tubes and thereby resist the inward
percolation of water.
Another part of our said invention relates to the valve spindle of low water safety
valves. According to this part of our said invention the valve spindle is made
hollow and has an internal prolongation extending to the low water level of the
water. When the water in the boiler is above the low water level the hollow
spindle will be filled with water which will be cooled by the air acting on that part
of the spindle which is outside the boiler. Should the water descend below the
orifice of the internal prolongation of the hollow valve spindle steam will enter
and by heating the valve spindle will cause it to expand longitudinally. The valve
and its seating are so arranged and combined with the spindle that on the latter
becoming longer on the entrance of steam the valve opens. Such a valve and
spindle may be indenendent of the float or may be combined therewith in such a
way that in case the float fails to open the valve the expansion spindle may do so or
vice versa.
In some cases a spring is combined with the valve spindle so as to keep or aid
in keeping the valve to its seating until opened by the descent of the water below
the low water level. An adjusting stop or abutment bearing against the end of the
expansion spindle enables the range of the valve on the expansion of the spindle to
be accurately adjusted to any particular case.
1000

page_text: COMPLETE SPECIFICATION.
Improvements in or applicable to Low Water Safety Valves for Steam
Boilers.
F.
We, JAMES ASIITON FLETCHER and SAMUEL FLETCHER, both of Borough Brass
Works, Ashton-under-Lyne, Brass Founders, 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:-
Our said invention relates to improvements in or applicable to low water safety
valves that is to say valves which automatically open and permit the escape of
steam in the event of the water level sinking too low. In order that our invention
may be more clearly understood we will describe the same with reference to the
accompanying drawings.
DESCRIPTION OF DRAWINGS.
Fig. 1 is an elevation partly in section of a combined low water and high steam
safety valve fixed in position on a boiler.
Fig. 2 is an enlarged view of the low water valve and seating.
Fig. 3 is an elevation (at right angles to Fig. 1) of the pillars and cross bar
carrying the valve spindle.
Fig. 4 is a similar view with only a single spring.
Fig. 5 is a similar view with springs above and below the cross bar.
Fig. 6 is an elevation at right angles to Fig. 1 of the float.
According to our said invention the valve spindle a of the low water valve is made
hollow and has a prolongation a' inside the boiler extending to the low water level
of the boiler. The part a forms a separate piece secured by flanges and bolts or
otherwise to the main spindle a. By this construction the valve may not only be
more readily made available for different kinds of boilers but the further advantage
is presented that in the event of the part al becoming so far corroded by the action
of some kinds of water as to require replacing it is only necessary to renew the
part a¹.
On the valve spindle a we form or attach a valve a³ which normally takes against
a seating a³ in the valve casing. The upper part of the valve spindle is screwed
at a into a cross bar b carried by springs 61 on pillars 62. The springs 61 are in
compression and normally tend to press the cross bar b upwards and against the
nuts b³ on the screwed ends of the pillars. The nuts 6 thus form adjustable abut-
ments and they are so regulated that when the valve should close the springs cau
pull the valve upwards against its seating.
When the water in the boiler is 'above the low water level the hollow spindle will
be filled with water which will be cooled by the air acting on that part of the
hollow spindle which is outside the boiler. Should the water descend below the
end of the part a steam, will enter and will heat the hollow spindle a causing it to
expand lengthwise. The nuts 63 prevent the spindle rising and consequently it can
only elongate in a downward direction when the valve a² will be removed from its
seating and steam can escape.
Fig. 4 shows a modification in which the valve is supported by a single spring
surrounding the valve spindle instead of two side springs. In this case a bearing
cap c is provided which takes against an abutment screw b in the fixed cross bar 65
Fig. 5 shows a further modification in which a sliding cross bar b is combined
with lifting springs 6 below and buffer springs 66 above. Adjustable abutment
nuts 63 (as in Fig. 3) are provided for limiting the upward expansion of the hollow
spindle a. In this construction instead of the spindle bearing against a rigid

page_text: abutment when expanding it hears against a slightly yielding buffer and this
gives a greater power of adjustment to suit the greater expansion which takes place
with the high steam pressures and the consequent higher temperatures which are
now coming more into use. Such a valve and spindle as described may be used by
itself or may be combined with a float as shown in Fig. 1 so that in case the float
fails to open the low water safety valve the expansion spindle may do so or
vice versa. In this combination d is a lever having its fulcrum at and a projection
at d' which takes against a bearing plate d³ attached to the hollow spindle a:
A float e is suspended from the lever d and balanced by a balance weight in
the usual manner. On the float descending below any determined point the
projection d will pull the valve spindle a downwards compressing the springs bl b¹
and permitting the steam to escape. The float may be of any usual construction.
We prefer however to make it of a number of hermetically sealed tubes e¹ assembled
together and secured by plates and bolts as shown in Figs. 1 and 6 so as to form a
kind of raft. In some cases we seal up water in the tubes el which on vapourising
under the action of the surrounding heat will produce an internal pressure to
counterbalance the external pressure and thereby resist the inward percolation of
water.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is:
1. A low water safety valve consisting of a hollow expansion valve spindle having
a valve formed thereon which takes directly against a valve seating substantially
as hereinbefore set forth and described and shown in the accompanying drawings.
2. The combination with an expansion low water safety valve such as described
of a lever and float substantially as set forth and described with reference to Fig. 1
of the accompanying drawings.
Dated this 9th day of June 1897
E. T. WHITELOW, A.M. Inst., C.E.
70 Deansgate, Manchester, Agent for the Applicants.