IMPROVEMENTS IN SAFETY VALVES
Year: 1884

page_text: We WILLIAM NEWZAM NICHOLSON and ARTHUR THOMAS ALLCOCK of
Newark upon Trent, in the County of Nottingham, Engineers, do hereby declare
the nature of our Invention for IMPROVEMENTS IN SAFETY VALVES, and in what
manner the same is to be performed, to be particularly described and ascertained in
and by the following statement:
Our Invention is for improvements in safety valves; whereby they are so
constructed that should any additional weight be placed upon the valve, beyond.
that at which it is fixed to blow off, such overweight will cause the valve to open
and give an immediate warning, and continue to release the steam until the
overweight is removed.
In the appended Sheet of Drawings Figure 1 is a side elevation of the valve.
detached from its seat. Figure 2 is a longitudinal section and Figure 3 is a plan
of the underside of a complete safety valve made in accordance with our Invention.
It consists of a compound valve made up of the annular valve A opening outwards.
from its seat a, and an internal central valve B closing the annulus and opening
inwards from its seat b. The inner central valve B is provided with a spindle Č
projecting through the annular valve A and furnished with a loose collar D and
an adjusting nut d for regulating the pressure of a spiral spring S which bears
with one extremity against the collar D and with its other end against the annular
valve A, so tending to hold the internal valve B up to its seat b on the annular
valve A with a force equal to that which is required to hold the whole compound
valve down on its seat a against the pressure of the steam in the boiler. The
compound valve so formed is weighted down to its seat a by a lever L with
a weight or spring W of ordinary construction, which presses on the head of the
spindle C of the inner central valve B; this pressure is transmitted through the
spiral spring S to the annular valve A, and so long as it does not exceed that of
the spring S the compound valve A and B will act as an ordinary safety valve.
Should however the pressure applied by the lever L exceed that of the spring S
the annular valve A will be held down to its seat a, the spring S deflected and the
inner central valve B opened inwards and the steam allowed to escape.
For the purpose of further calling attention to the escape of steam due to over-
weighting the lever L, the dome of a whistle H may be attached to the valve
spindle C having its edge over the central hole of the annular valve A so that it
may be sounded by the escape of steam from the valve B and an audible warning

page_text: given of the overweighting. Although the drawing shows the valve to be weighted
by means of the lever L and a weight or spring W it is obvious that either of the
latter can be applied direct to the valve spindle C without the intermediate
lever L, in any of the methods in ordinary use.
The compound valve A and B and its spring S are enclosed in a case E fastened
to the base plate F and secured by a lock K so that the spring S after having
been adjusted to the required pressure cannot be tampered with.
For the purpose of enabling the annular valve A to be rotated on its seat a, one
or more stops N are formed on or fixed to the bottom of the valve B they engage
with corresponding stops N₁ formed on the annular valve A and which also form
guides to direct it on its seat a.
By rotating the valve spindle C the stops N come in contact with the stops N¹
on the annular valve A and so turn it on its seat a, also allowing an interval for
the valve B to rotate on its own seat b.
Having now particularly described and ascertained the nature of the said
Invention and in what manner the same is to be performed we declare that what
we.claim is:-
.
1. The construction of the compound valve, consisting of the annular valve A,
the internal central valve B and its spindle C with the spring S or its equivalent,
substantially as shown, and for the purposes described, or any mere modification
thereof.
2. The combination of a compound valve so formed with the whistle H sub-
stantially as shown and for the purposes described, or any mere modification
thereof.
3. The employment of one or more stops N and N' in combination with the
internal central valve B and the annular valve A, substantially as shown and for
the purposes described, or any mere modification thereof.
th 1
WILLIAM NEWZAM NICHOLSON.
ARTHUR THOMAS ALLCOCK.