IMPROVEMENTS IN SAFETY VALVES
Year: 1871

page_text: LETTERS PATENT to Edward Field, of Chandos Chambers, Adelphi,
in the City of Westminster, Consulting Engineer, and Lewis
Olrick, of No. 27, Leadenhall Street, in the City of London,
Consulting Engineer, for the Invention of "IMPROVEMENTS IN SAFETY
VALVES."
Sealed the 1st September 1871, and dated the 20th April 1871.
PROVISIONAL SPECIFICATION left by the said Edward Field and
Lewis Olrick at the Office of the Commissioners of Patents, with
their Petition, on the 20th April 1871.
We, EDWARD FIELD, of Chandos Chambers, Adelphi, in the City
of Westminster, Consulting Engineer, and LEWIS OLRICK, of No. 27,
Leadenhall Street, in the City of London, Consulting Engineer, do
hereby declare the nature of the said Invention for "IMPROVEMENTS IN
SAFETY VALVES," to be as follows:-
-:
The object of our improvements in safety valves is to render such
valves more efficient and reliable in working than heretofore, for which
purpose in constructing spring balance safety valves according to our
Invention we interpose between the spring and the valve as herein-after
described a differential lever or levers of the third order operating in

page_text: such manner as without any material degree of friction upon the fulcrum
pin of the lever to reduce the leverage when the differential lever or
levers is or are being raised by the valve, and thereby to counterbalance
or neutralise the additional downward strain, which would otherwise be
put on to the valve by the action of the spiral spring.
Our Invention further consists in making such safety valves with
annular openings or ways so as to afford more ready means of escape
for surplus steam with a moderate lift of valve, and in the application
of a small hand lever, either upon the fulcrum pin of the differential
lever, or upon a separate fulcrum pin, in such manner as to enable the
valve to be raised by hand from its scat, so as to ascertain whether
the valve is free and does not stick, but so, nevertheless, as to prevent
the hand lever from being used for holding the valve down upon its seat.
A main defect in spring balance safety valves as commonly con-
structed is, that owing to their small lift and long leverage the gradually
increasing strain which is put upon the spring balance as the valve
rises results in a considerable addition to the steam pressure in the
boiler after the steam has commenced issuing from the valve, and
consequently the steam pressure in the boiler, instead of being main-
tained at or about the pressure to which the valve is set is increased
to a very large and dangerous extent above the pressure to which the
valve is set, and at which the steam ought therefore to commence
blowing off. Now we obviate this serious evil by the reduction of the
leverage when the differential lever or levers is or are being lifted by
the valve, so as to counterbalance or neutralize the additional down-
ward strain put on to the valve thro' the lever by the balance spring
as described. The differential lever works on a fulcrum pin having
bearings in the valve case or body, with suitable provision for lubrica-
tion; and the lower part or shorter arm or branch of the differential
lever is formed to receive and rests upon the pointed or coned end of
a short pin, which occupies a recess in the valve, the lower end of the
pin being pointed or coned like its upper end, and resting in the lower
part of the recess in the valve specially formed to receive it, so that
this double pointed pin while being allowed sufficient play to efficiently
fulfil its offices, is by its peculiar situation within the recess in the
valve prevented from slipping out of its place laterally and so being
thrown out of gear with the lever, and joints being dispensed with
all friction is avoided. The upper or longer part or branch of the

page_text: differential lever is formed to receive a knife edge formed with or
attached to a suitable frame, in whose other end there is a hole or way
thro' which the adjusting screw passes. To this screw is attached
one end of the spiral spring, its other end being secured to a fixed
transverse pin or bar, which we call the tension pin or bar. The upper
end of the screw is provided with a suitable nut, bearing at its under
part against the upper end of the frame, so that by tightening this nut
and thereby extending the spiral spring the frame is forced down, and by
the operation of its knife edge upon the upper or longer part or branch
of the differential lever causes the lower part or shorter arm or branch
thereof to communicate the requisite downward pressure through the
double pointed pin to the valve, which is by preference made with
a V-shaped face or faces resting upon a flat scat or seats. The valve
case or body extends to within a short distance of the upper end of the
scrow, and is formed or provided with an arm or a bracket carrying a
gauge, upon which the pressure at which the valve is set is indicated
by the position of the upper end of the screw, which passes very freely
through a guide for preventing any considerable lateral movement of
the screw.
It will be obvious that the differential lever instead of being made
in one piece may be constructed in parts separately attached to the
fulcrum pin, and may be used in conjunction with an ordinary circular
valve instead of the annular valve herein-before described.
Also that safety valves constructed according to our Invention besides
being used for steam boilers are also applicable to other vessels con-
taining gases under pressure.
In valves constructed with our improvements the valve is prevented
from flying off in the event of any injury to the spring, the only result
of its giving way being to permit the escape of the steam or gas from
the boiler or other vessel.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Edward Field and Lewis Olrick in the Great Seal
Patent Office on the 20th October 1871.

page_text: Consulting Engineer, and LEWIS OLRICK, of No. 27, Leadenhall Street,
in the City of London, Consulting Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twentieth day of April, 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 Edward Field and Lewis Olrick, Ier
special license that we, the said Edward Field and Lewis Olrick, our
executors, administrators, and assigns, or such others as we, the said
Edward Field and Lewis Olrick, our exccutors, 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 Kingdom of Great Britain and Ireland, the Channel Islands,
and Isle of Man, an Invention for "IMPROVEMENTS IN SAPETY VALVES,"
upon the condition (amongst others) that we, the said Edward Field
and Lewis Olrick, our executors or administrators, by an instrument
in writing under our, or their, or one of our or their hands and seals,
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 Seal Patent Oflice within six calendar
months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that we, the said Edward Field and Lewis Olrick,
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, reference being had to the
accompanying Sheet of Drawings, which forms a part of this Specifi-
cation, and in which Fig. 1. is a vertical section of a spring balance
safety valvo constructed with our improvements; Fig. 2 is a section at
right angles to the foregoing; Fig. 3 is an outside view; Fig. 4 is a
plan; Fig. 5 is a section through the line C, D, of Fig. 2; Fig. 6
is a plan of the annular valve; and Fig. 7 is a section through the
line A, B, of Fig. 1.
'
The object of our improvements in safety valves is to render such
valves more efficicnt and reliable in working than heretofore, for which
purpose in constructing spring balance safety valves according to our
Invention we interpose between the spring a and the valve bas herein-

page_text: after described, a differential lever c (or levers) of the third order
operating in such manner as without any material degree of friction
upon the fulcrum pin d of the lever to reduce the leverage when the
differential lever (or levers) is (or are) being raised by the valve, and
thereby to counterbalance or neutralise the additional downward strain
which would otherwise be put on to the valve by the action of the spiral
spring.
1
Our Invention further consists in making such safety valves with
annular openings or ways e so as to afford moro ready means of escape
for surplus steam with a moderate lift of the valve b, and in the appli-
cation of a small hand lever f either upon the fulcrum pin d of the
differential lever c or upon a separate fulcrum pin in such manner as to
enable the valve b to be raised by hand from its scat so as to ascertain
whether the valve is free and does not stick when steam is up in the
boiler to which the valve is attached, but so, nevertheless, as to prevent
the hand leverf from being used for holding the valve b down upon its
seat. A main defect in spring balance safety valves as commonly
constructed is that owing to their small lift and long leverage the
gradually increasing strain which is put upon the spring balance as the
valve rises results in a considerable addition to the steam pressure in
the boiler after the steam has commenced issuing from the valve, and
consequently the steam pressure in the boiler instead of being main-
tained at or about the pressure to which the valve is set, is increased to
a very large and dangerous extent above the pressure to which the valve
is set, and at which the steam ought therefore to be blowing off to a
sufficient extent to prevent the,accumulation in the boiler of a greater
pressure than that at which the valve is set. Now wo obviate this
serious evil by the reduction of the leverage when the differential lever o
(or levers) is (or are) being lifted by the valve 6 so as to counterbalanco
or neutralize the additional downward strain put on to the valve
through the lever c by the balance spring a as described. The differ-
ential lever c works on a fulcrum pin d having bearings in the valve
case or body g with suitable provision for lubrication as shewn, and the
lower part or shorter arm or branch of the differential lever is formed
to receive and rests upon the pointed or coned end of a short pin h
which occupies a recess in the valve b, the lower end of the pin being
pointed or coned like its upper end and resting in the lower part of the
recess in the valve specially formed to receive it as shewn, so that this
double-pointed pink while being allowed sufficient play to efficiently

page_text: fulfil its offices is by its peculiar situation within the recess in the
valve prevented from slipping out of its place laterally and so being
thrown out of gear with the lever c, and joints being dispensed with all
friction is avoided. The upper or longer part or branch of the
differential lever c is formed to receive a knife edge i formed with or
attached to a suitable frame j, in the other end of which there is a hole
or way k through which the adjusting screw passes. To this screw/
is attached one end of the spiral spring a, its other end being secured to
a fixed transverse pin or bar m which we call the tension pin or bar.
The upper end of the screw is provided with a suitable nut n bearing
at its under part against the upper end of the frame j, so that by
tightening this nut n, and thereby extending the spiral spring a, the
frame is forced down, and by the operation of its knife edge i upon
the upper or longer part or branch c² of the differential lever c causes
the lower part or shorter arm or branch c¹ thereof to communicate the
requisite downward pressure through the double-pointed pin / to the
valve b, which is by preference made with V-shaped faces resting upon
flat seats as shown. The valve case or body g extends to within a short
distance of the upper end of the screw 1, and is formed or provided with
an arm or a bracket o carrying a gauge p upon which the pressure at
which the valve is set is indicated by the position of the upper end of
the screw, which passes very freely through a guide in o as shown for
preventing any considerable lateral movement of the screw.
It will be obvious that the differential lever c instead of being made
in one piece may be constructed in parts separately attached to the
fulcrum pin d, and may be used in conjunction with an ordinary circular
valve instead of the annular valve herein-before described. Also that
safety valves constructed according to our Invention besides being
used for steam boilers are also applicable to other vessels containing gases
under pressure.
In valves constructed with our improvements the valve is prevented
from flying off in the event of any injury to the spring a, the only result
of its giving way being to permit the escape of the steam or gas from
the boiler or other vessel. 7 is a ferrule which is placed around the
lower part of the screw / underneath the cyo k of the frame j and resting
on the shoulder or swelled eye of the screw for the purpose of pre-
venting the valve from being tampered with or screwed down to a
higher pressure than that at which the boiler is intended to be worked.

page_text: And having now described the nature of our said Invention, and in
what manner the same is to be or may be performed or carried into
practical effect, we hereby declare that we do not claim as of our Inven-
tion or the exclusive use of the several parts herein-before described and
referred to, except when the same are employed in and for our said
Invention, which we hereby declare to consist in the combination of
parts forming the improved safety valve constructed and arranged as
herein-before described and illustrated in the accompanying Drawings.
In witness whereof, we, the said Edward Field and Lewis Olrick,
have hereunto set our hands and seals, this Twentieth day of
October, in the year of our Lord One thousand eight hundred and
seventy-one.
EDWARD FIELD. (L.S.)
LEWIS OLRICK.
(L.S.)