Improvements in Steam and Low Water Safety Valves.
Year: 1893

page_text: Date of Application, 16th Feb., 1893—Accepted, 8th Apr., 1893
COMPLETE SPECIFICATION.
Improvements in Steam and Low Water Safety Valves.
I, ALEXANDER TURNBULL of St. Mungo Works, Bishopbriggs, in the County
of Lanark, North Britain, 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 :-
The object of this invention is to provide simple and efficient devices which act
automatically to prevent damage to the boiler in case the water should fall too low
or the pressure of steam should exceed the maximum.
In order that my invention may be properly understood and readily carried into
effect have hereunto appended two explanatory sheets of drawings in the
several figures of which corresponding parts are marked with the same letters of
reference.
Figure 1 represents a section of one part of the boiler with a sectional elevatio
of one modification of my invention.
Figures 2 and 3 represent other modifications when my invention is used as a low
water safety valve which can discharge all the steam generated in the boiler.
According to the modification represented in Figure 1 I form on the upper
surface of the weighted steam safety valve Z a valve seat for carrying a second
smaller valve E. This valve is held down by a spring in a chamber formed in the
interior of an enlarged spindle of the larger valve. To the valve E a rod D is
attached having a weight X at its lower end to keep it vertical and the valve E
properly bedded on its seat. Inside the boiler I provide a beam A A, pivoted
at a, which has a float B hanging from one end and a counterpoise Changing
from the other. The rod D attached to the valve E has a slot formed in it, in
which a pin a¹ in the beam A A works. When the water in the boiler is at the
proper level the pin a¹ is somewhere between the top and bottom of the slot, but
should the water fall too low the float descends and the pin a¹ rises and presses
against the top of the slot. When this pressure exceeds the force by which the
valve E is kept closed the valve is opened and all the steam is allowed to escape.
Should the steam pressure in the boiler rise above the maximum the large valve Z
is lifted and carries the small valve E with it, but owing to the slot in the rod D
the beam does not in any way keep the two valves from lifting together. Although
the valve E is not intended ordinarily to act as a high pressure safety valve, it is
obvious that should the large valve Z become fast in its seat the valve E is free to
work as an independent high pressure safety valve.
Figure 2 illustrates my invention when applied as a low water safety valve alone,
with a valve opening outwards and kept closed by a lever, float, and weight
arrangement in the interior of the boiler.
Figure 3 is a valve opening inwards and kept closed by a lever, weight, and also
by the pressure of steam in the boiler.
Inside the boiler I provide a beam A A, pivoted at a, which has a float B hanging
from one end and a counterpoise Changing from the other. A rod D attached to
the valve E is pivoted at a to the beam A. and is carried down below the pivot and
terminates in a ball or weight X, so as to bring the centre of gravity well below
the pivot and cause the rod to stand vertically.
In Figure 2 when the water falls too low the float B falls with it, and the
point a' rises and carries the rod D up, which opens the valve and allows the steam
to escape. In Figure 3 when the float B falls the point a' descends carrying the
rod D and valve E with it, and allows the steam to escape. The displacement of
the float B and the weight of the counterpoise C must be adjusted for the area of
the valve and the pressure at which the boiler is to be worked.

page_text: 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 :-
1. The combined steam and low water safety valve substantially as described
and illustrated on Sheet 1, Figure 1 of the accompanying drawings.
2. The low water safety valve for discharging all the steam in the boiler when
the water falls below a safe level, substantially as described and illustrated on
the accompanying drawings Figures 2 and 3.
Dated this 15th day of February 1893.
BOTTOMLEY & LIDDLE,
154, St. Vincent Street, Glasgow, Applicant's Agents.