IMPROVEMENTS IN SAFETY VALVES
Year: 1871

page_text: LETTERS PATENT to Samuel Wilkinson Snowden and James Moffat,
both of Barking, in the County of Essex, Engineers, for the
Invention of "IMPROVEMENTS IN SAFETY VALVES."
Sealed the 25th August 1871, and dated the 27th February 1871.
PROVISIONAL SPECIFICATION left by the said Samuel Wilkinson
Snowden and James Moffat at the Office of the Commissioners of
Patents, with their Petition, on the 27th February 1871.
We, SAMUEL WILKINSON SNOWDEN and JAMES MOFFAT, both of
Barking, in the County of Essex, Engineers, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN SAFETY VALVES," to be
as follows:-
The object of our Invention is the application of a safety valve which
will admit of a sufficient lift so as to carry away the steam, and also
when applied to vessels prevent the valve from canting in a seaway, also
at the same time giving greater facility for lifting by hand.
It is constructed as follows:-The fulcrum on the lever is moveable,
that is, the fulcrum pin works in an upright slot. At or beyond the

page_text: fulcrum we suspend or otherwise attach a weight or weights for balancing
half the steam pressure on the valve. A weight is also applied to the
other end of the lever for balancing the other half of the steam pressure;
as soon as the pressure gets in excess the lever lifts up bodily and not
in a slanting direction, as with ordinary lever valves, thereby admitting
of a large lift without any larger lift at the end of the lever. When the
valve wants to be "cased " by hand in the usual way, the power being
applied at the end opposite the fulcrum end, much greater facility is
afforded for, doing so, as only half the weight has to be lifted as soon as
the fulcrum pin on the lever being raised a very short distance bottoms
in its slot. In the case of the weight being applied beyond the fulcrum
as soon as the fulcrum pin on the other end of the lever being raised a
very short distance bottoms in its slot the weight there assists the lifting
of the valve. In the case of the weight applied at the fulcrum the
lifting of the valve by hand is only facilitated to the extent of half the 1
usual weight.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Samuel Wilkinson Snowden and James Moffat in
the Great Seal Patent Office on the 25th August 1871.
TO ALL TO WHOM THESE PRESENTS SHALL COME, wc, SAMUEL
WILKINSON SNOWDEN and JAMES MOFFAT, both of Barking, in the
County of Essex, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
'Letters Patent, bearing date the Twenty-seventh day of February, in the
year of our Lord One thousand eight hundred and seventy-one, in the
thirty-fourth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto us, the said Samuel Wilkinson Snowden and James
Mollat, Her special license that we, the said Samuel Wilkinson Snowden
and James Moffat, our executors, administrators, and assigns, or such
others as we, the said Samuel Wilkinson Snowden and James Moffat, our
executors, administrators, and assigns, should at any time agree with, and
no others, from time to time and at all times thereafter during the term
therein expressed, should and lawfully might make, use, exercise, and
vend, within the United Kingilom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN. {

page_text: SAFETY VALVES," upon the condition (amongst others) that we, the said
Samuel Wilkinson Snowden and James Moffat, our exccutors or ad-
ministrators, by an instrument in writing under our or their hands and
scals, or under the hand and seal of one of us or them, should particularly
describe and ascertain the nature of the said Invention, and in what
manner the same was to be performed, and cause the same to be filed
in the Great Scal Patent Office within six calendar months next and
immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Samuel Wilkinson Snowden, ou
behalf of myself and the said James Moffat, do hereby declare the nature
of the said Invention, and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following
statement thereof, that is to say :-
The object of our Invention is the application of a safety valve which
will admit of a sufficient lift so as to carry away the steam, and also
when applied to vessels to prevent the valve from canting in a seaway,
also at the same time giving greater facility for lifting by hand.
For these purposes in place of employing a weighted lever turning on
a fixed fulcrum at one end to hold down the safety or escape valve, the
ordinary pin or fulcrum of the lever is arranged so that it may rise and
fall in a slot in a suitable fixed guide, and on each arm of the lever
weights are applied so as to balance one another and form a weighted
scale beam resting at its pivot on the top of the valve. By thus holding
down the valve by a weighted scale beam resting upon it the weighted
lever will be lifted up bodily when the pressure on the valve gets in
excess, thereby admitting of a comparatively large lift of the valve.
without any great lift of either end of the weighted lover. When the
valve wants to be "eased" by hand in the usual way the lever may be
raised at either of its ends, and great facility is afforded for doing so as
the weights are balanced on the beam, and so soon as by raising one armi
of the lever the opposite arm is depressed on to a fixed stop only one-
half of the weight on the valve will have to be lifted.
In the Drawing hereunto annexed I have shewn a vertical section of
a safety valve arranged as above described. The safety valve shewn is
suitable for being applied to the boilers of steam vessels.
a, a, is the outer casing of the safety valve.
to the top of the steam space of the boiler, so
This casing is bolted on
that the pipe b which

page_text: rises up into the casing is filled with steam from the boiler. The top of
the pipe is closed by the valve c, upon which rests the lever or scale
beam d, having weights e, e, balanced upon its two arms. f is a pin
carried by one arm of the lever; this pin works in slots in a pair of
fixed uprights g, between which the arm of the lever is free to rise and
fall. The opposite end of the lever similarly passes between two upright
guides h, between which it is just free to rise and fall freely. At the
centre of the lever or scale beam d is a pink which passes through
slots in a fork on the end of a rod 1. This rod passes down through
the top of the casing a, and is jointed to an arm m³ on an axis m, so
that by turning this axis by a lever arm upon it or otherwise the
weighted lever d can be raised whenever the valve may require to be
eased. The weights e being balanced on the opposite arms of the
lever it will be seen that even if the lever is in a position crosswise of
a vessel the rolling of the vessel will not affect the weight upon the
valve c, and no improper escape of steam will take place from the safety
valve owing to the rolling of the vessel as is now frequently the
case. When the pressure of steam in the boilers gets in excess the
valve, together with the weighted beam resting upon it, is lifted, and
the steam escapes into the casing a, and passes away through the

page_text: Having thus described the nature of our Invention, and the manner
of performing the same, we would have it understood that what we
claim is, the combined arrangement of safety valve substantially as
herein described.
In witness whereof, I, the said Samuel Wilkinson Snowden, have
hereunto set hand and seal, this Twenty-fifth day of August,
in the year of our Lord One thousand eight hundred and seventy-
onc.