IMPROVEMENTS IN SAFETY VALVES
Year: 1876

page_text: LETTERS PATENT to Martyn John Roberts, of the City of Bath, Esquire,
for the Invention of "IMPROVEMENTS IN SAFETY VALVES,"
CALL
NAKA
PROVISIONAL SPECIFICATION left by the said Martyn John Roberts, at the
Office of the Commissioners of Patents on the 29th August 1876.
MARTYN JOHN ROBERTS, of the City of Bath, Esquire. "IMPROVEMENTS IN SAFETY
VALVES."
The objections to steam boiler relief or safety valves as at present constricted are
well known. When they rise from their seats to allow of the escape of steam they
do so in such a slight degree that they fail to relieve the boiler from excessivo
pressure. They require to be held down by heavy weights or by strong springs, the
former of which are cumbrous, and strain their spindles, and for marine boilers are
comparatively useless by reason of their varying pressure consequent upon the ship's
rolling, while the latter do not give way easily, and their power increases as the
valve rises although the pressure of the steam decreases, further, seated safety
valves are liable to stick to their seats.
Now, according to the first part of my Invention, I construct a steam relief valve,
which is a true safety valve, it will afford any desired amount of opening for the
escape of steam; it requires no weight or metallic spring to keep it shut, and
being constantly in motion it cannot stick to its seat; it can also be set so as
to open at any desired pressure of steam, a property which is valuable for marine
engines.
My valve is constructed as follows:-A pipe is fitted, preferably outside the
boiler; it extends downwards, about two feet more or less, and is in connection
at its top with the steam space of the boiler, and it may also be in connection
with the water in the boiler. The downward extension of the pipe is for the
purpose of maintaining the water in it at a moderate heat so as not to in-
juriously affect the flexible disc herein-after mentioned. At the bottom of this
pipe is a chainber or enlargement, in which is fitted a disc of india-rubber or
other suitable flexible material, and to this disc is fixed a rod extending up to the
steam space where it is fixed to a small slide valve, which when open gives

page_text: passage for the steam into the open air. Below the disc is a water space, in which
is a hollow ball or bag of india-rubber or other flexible and air-tight material, and
this bag (there may be one or several) is surrounded by water From that portion
of the pipe which is above the disc, to the portion below the disc, there is a
communicating pipe provided with a tap or cock which can be shut or opened at
pleasure.
The action is as follows:-The tap being opened the pipe and the chamber or en-
largement at the bottom thereof are filled with water; steam is then raised in the
boiler until the maximum pressure desired is obtained; this presses on the surface of
the water in the pipe and thus compresses the air in the bag to a corresponding degree.
While the boiler steam is being raised to the desired pressure with the tap open,
the flexible disc remains unmoved, because the pressure is equal on each of its sur-
faces. The tap is now shut and the safety valve is ready to act. Any difference
between the pressure upon the top surface of the disc and that on its bottom surface
will immediately cause the disc to move. An increase in pressure causes it to
descend, and in its descent it pulls the valve rod and slides the valve open, thereby
allowing steam to escape. As the pressure in the boiler and on the flexible disc falls
below its normal degree the higher pressure in the bag acts upon the under surface
of the disc, raising it, and thereby sliding the valve shut.
If at any time it be required to reduce or increase the working steam pressure in
the boiler and at the same time adjust the safety valve to a proper action at that
altered pressure it is only necessary to open the tap, to keep it open until the desired
pressure is attained, and then to shut it.
In a modified arrangement of my valve I dispense with the bag and connect a
vertical pipe to the chamber or enlargement before described, so that when the tap
is opened water fills the enlargement and rises in the vertical pipe until the air in
its head becomes so compressed that it balances the steam pressure. The tap is then
closed and the flexible disc comes into action as before. In order to reduce the
absorption of the air by the water I diminish as much as possible the extent of
water surface in contact with the air by placing a float thereon.
Another part of my Invention consists in constructing a seated safety valve
which has no levers, spindles, guides, joints, bearings, or other parts liable to obstruct
the rising of the valve or to get deranged, which can be kept shut by means of a
very small weight, and which will offer a larger opening for the escape of steam
than any known valve, and allow of such opening taking place gradually and there-
fore safely. A large valve constructed according to the old method requires an
enormous weight or very powerful spring to keep it shut; for example, a valve
having a diameter of 5 inches, and therefore an area of upwards of 19 square inches,
requires with a steam pressure of 60 lbs. a weight of 1,178 lbs. to keep it shut.
Now I employ a series of valves of comparatively very small diameter, say one inch,
each composed of a disc preferably of an oblong or oval shape on a seat as usual; it
has no spindle or guide, but is rivetted or fixed to one end of a flat spring or other
flexible holder, arm, or support, the other end of which is rivetted or fixed to the
boiler. The spring being wide, say 6 inches, there can be no lateral motion of the
valve, and consequently it does not require a spindle or guide to make it fall true
on its seat, and the rise and fall of the valve being simply by the bending of its
holder, arm, or support, there are no pins, joints, or moving parts to stick or rust,
and as the area of the valve is only 0-7854 of an inch, it will only require at CO lbs.
pressure 47 lbs. to keep it closed instead of 1,178 lbs. as before mentioned for a 5 inch
valve. Now the opening afforded by a seated valve is a cylinder whose length is
equal to the lift of the valve, and whose diameter is equal to that of the valve, and
taking the lift to be the same in both cases the opening is as the respective
diameters. Thus a 5-inch valve has a circumference of 15 inches, and a one inch
valve a circumference of 3 inches, and it will require 5 one-inch valves to give
an equal escape to one of 5 inches. But the respective areas differ greatly, viz.,
the 5-inch valve, whose exact area is 19-635, will require 1,178 lbs. to keep it down
at a pressure of 60 lbs. as before mentioned, while the 5 one-inch valves, offering as

page_text: large an opening for steam escape, can be kept down by 47 lbs. on each. Further
the 5-inch valve opens at once to its full extent, and often produces too sudden and
dangerous an escape of steam if the valve be of large diameter, but by employing a
series of 5 of my small valves each may be loaded to a different pressure, so that
they will open one after the other and give a gradual and efficient relief to the
boiler. Or by having a larger number of small valves the opening for steam escape
can be increased; or fewer may be employed if 5 are not necessary. The small
valves may be arranged in line upon the boiler or compactly in a circle, the
respective springs or other bolders to which they are rivetted, as before described,
meeting in the centre and being placed one over another, or they may be arranged
in any other suitable manner The valves will not require separate openings into
the boiler, but may be placed upon a pipe having one hole only into the boiler.
When it is thought desirable to multiply or increase the power of the dead weight
or spring (which retains the valve closed) by aid of a lever, I attach the lever at
once to the valve, or it may be detached and press on the back of the valve, but in
either case I avoid the use of pins or edges moving in or upon bearings and support
the said lever by a flexible ain in the same manner as the valve itself is supported
I also sometimes use a form of valve which is superior to that of the old flat bottom
valve, inasmuch as the new form avoids in a great measure the evil of "minus
pressure," and this my improved form is that of an open box placed mouth down-
wards upon a seat; or sometimes I use a raised ring or bearing upon the boiler, and
the valve just described rests upon the ring or bearing so that a sufficient space
exists for the escape of steam between the raised ring or bearing and the sides of
the box.
I also sometimes use asbestos, india-rubber, or other elastic substance which cannot
be destroyed by the heat of the steam as a seat for safety valves.
The spring or other flexible holder to which the valve is attached as herein-before
described, although specially intended for safety valves when employed in a series,
is applicable to single valves.
SPECIFICATION in pursuance of the Conditions of the Letters Patent, filed by
the said Martyn John Roberts, in the Great Seal Patent Office on the 28th
February 1877.
MARTYN JOHN ROBERTS, of the City of Bath, Esquire. "IMPROVEMENTS IN SAFETY
VALVES."
The objections to steam boiler relief or safety valves as at present constructed are
well known. When they rise from their seats to allow of the escape of steam, they
do so in such a slight degree that they fail to relieve the boiler from excessive
pressure. They require to be held down by heavy weights or by strong springs,
the former of which are cumbrous and strain their spindles, and for marine boilers
are comparatively useless by reason of their varying pressure consequent upon the
ship's rolling, while the latter do not give way easily, and their power increases as
the valve rises, although the pressure of the steam decreases; further, seated safety
valves are liable to stick to their seats
Now according to the first part of my Invention I construct a steam relief valve
which is a true safety valve, it will afford any desired amount of opening for the
escape of steam, it requires no weight or metallic spring to keep it shut, and being
constantly in motion it cannot stick to its seat; it can also be set so as to open at
any desired pressure of steam, a property which is valuable for marine engines.
My valve is constructed as follows:-A pipe is fitted preferably outside the
boiler, it extends downwards about two feet more or less, and is in connection at
its top with the steam space of the boiler, and it may also be in connection with
the water in the boiler. The downward extension of the pipe is for the purpose of

page_text: maintaining the water in it at a moderate heat so as not to injuriously affect the
flexible disc heroin-after mentioned. At the bottom of this pipe is a chamber or
enlargement, in which is fitted a disc of india-rubber or other suitable flexible
material, and to this disc is fixed a rod extending up to the steam space where it is
fixed to a small slide valve, which when open gives passage for the steam into the t
open air. Below the disc is a water space in which is a hollow ball or bag of
india-rubber or other flexible and air-tight material, and this bag (there may be
one or several) is surrounded by water From that portion of the pipe which is
above the disc to the portion below the disc, there is a communicating pipe provided
with a tap or cock which can be shut or opened at pleasure.
Before describing the action of this valve I will refer to Figure 1 of the annexed
Drawings, which is a representation of the same in vertical section; A represents
the boiler; B is a pipe communicating at its upper end with the steam space
of the boiler, and extending downwards as shown to a distance of, say 2 feet; C is a
chamber or enlargement at the bottom of the pipe B; and D is a disc or diaphragm of
india-rubber or other suitable flexible material dividing the chamber C horizontally;
E is a rod fixed to the disc D and carried up through the guides F, F, to the steam
space in the pipe B where it is fitted to a slide valve G. In the space below the
disc D is a hollow ball or bag H of india-rubber or other flexible and air-tight
material which is surrounded by water; I is a pipe communicating as shewn
between the pipe B and that portion of the chamber ḍ which is below the disc D;
K is a cock or tap on the pipe I.
The action is as follows:-The tap K being opened the pipe B and the chamber
or enlargement C are filled with water. Steam is then raised in the boiler until
the maximum pressure desired is obtained. This presses on the surface of the
water in the pipe B, and thus compresses the air in the bag H to a corresponding
degree. While the boiler steam is being raised to the desired pressure with the
tap K open, the flexible disc D remains unmoved, because the pressure is equal on
each of its surfaces. The tap K is now shut and the safety valve is ready to act.
Any difference between the preasure upon the top surface of the disc D and that
on its bottom surface will immediately cause the disc to move. An increase in
pressure causes it to descend, and in its descent it pulls the valve rod E and slides
the valve G open, thereby allowing steam to escape. As the pressure in the boiler
and on the flexible disc D falls below its normal degree, the higher pressure in the
bag H acts upon the under surface of the disc, raising it, and thereby sliding the
valve shut.
If at any time it be required to reduce or increase the working steam pressure in
the boiler, and at the same time adjust the safety valve to a proper action at that
altered pressure, it is only necessary to open the tap K to keep it open until the
desited pressure is attained and then to shut it.
In a inodified arrangement of my valve represented in Figure 2 I dispense with
the bag H and connect a vertical pipe L to the chamber or enlargement C, so that
when the tap K is opened, water fills the enlargement C and rises in the vertical
pipe L until the air in its head becomes so compressed that it balances the steam
pressure. The tap K is then closed, and the flexible disc D comes into action as
before In order to reduce the absorption of the air by the water, I diminish as
much as possible the extent of water surface in contact with the air by placing a
float M thereon.
Another part of my Invention consists in constructing a seated safety valve
which has no levers, spindles, guides, joints, bearings, or other parts liable to
obstruct the rising of the valve or to get deranged, which can be kept shut by
means of a very small weight, and which will offer a larger opening for the escape
of steam than any known valve, and allow of such opening taking place grad-
ually and therefore safely. A large valve constructed according to the old method
requires an enormous weight or very powerful spring to keep it shut; for example,
a valve having a diameter of 5 inches, and therefore an area of upwards of 19
square inches, requires with a steam pressure of 60 lbs. a weight of 1178 lbs. to keep
1

page_text: it shut. Now I employ a series of valves of comparatively very small diameter,
say one inch, each composed of a disc, preferably of an oblong or oval shape
on a seat, it has no spindle or guide, but is rivetted or fixed to one end of a flat
spring or other flexible holder, arm, or support, the other end of which is rivetted
oi fixed to a stud or support on the boiler, this flexible arm may be plated with
nickel or otherwise protected from oxidation. The spring being wide, say 6 inches,
there can be no lateral motion of the valve, and consequently it does not require a
spindle or guide to make it fall true on its seat, and the rise and fall of the valve
being solely guided by the bending of its holder, arın, or support, there are no pins,
joints, or moving parts to stick or rust; and as the area of the valve is only 07854
of an inch it will only require at 60 lbs pressure 47 lbs. to keep it closed instead of
1178 lbs as before mentioned for a 5 inch valve Now the opening afforded by a
seated valve is a cylinder whose length is equal to the lift of the valve, and whose
diameter is equal to that of the valve, and taking the lift to be the same in both
cases the opening is as the respective diameters; thus a 5-inch valve has a circum-
ference of 15 inches, and a one inch valve a circumference of 3 inches, and it will
require 5 one-inch valves to give an equal escape to one of 5 inches; but the re-
spective areas differ greatly, viz. :-the 5-inch valve whose exact area is 19 635 will
require 1178 lbs. to keep it down at a pressure of GO lbs. as before mentioned, while
the 5 one-inch valves offering as large an opening for steam escape can be kept
down by 47 lbs. on each. Further, the 5-inch valve opens at once to its full extent,
and often produces too sudden and dangerous an escape of steam if the valve be of
large diameter; but by employing a series of 5 of my small valves each may be
loaded to a different pressure so that they will open one after the other, and give &
gradual and efficient relief to the boiler; or by having a larger number of small
valves the opening for steam escape can be increased, or fewer may be employed
if 5 are not necessary. The small valves may be arranged in line upon the boiler
or compactly in a circle, the respective springs or other holders to which they are
rivetted as before described meeting in the centro and being placed one over another,
or they may be arranged in any other suitable manner; the valves will not require
separate openings into the boiler, but may be placed upon a pipe having one hole
only into the boiler.
When it is thought desirable to multiply or increase the power of the dead
weight or spring (which retains the valve closed) by aid of a lever I attach the
lever at once to the valve, or it may be detached and press on the back of the valve,
but in either case I avoid the use of pins or edges moving in or upon bearings, and
support the said lever by a flexible arm in the same manner as the valve itself is
supported.
I also sometimes use a form of valve which is superior to that of the old flat
bottomed valve inasmuch as the new form avoids in a great measure the evil of
"minus pressure," and this my improved form is that of an open box placed mouth
downwards upon a seat, or sometimes I use a raised ring or bearing upon the boiler,
and the valve just described rests upon this ring or bearing so that a sufficient
space exists for the escape of steam between the raised ring or bearing and the sides
of the box.
Figure 3 is a vertical section, and Figure 4 a plan of a safety valve of box form
as herein-before described, the said valve being rivetted or fixed to one end of a flat
spring or flexible holder also as herein-before described; A is the valve seat, B is the
box shaped valve, or what I may term a chambered valve; it has no spindle, guide,
or wings; C is the flat spring or flexible holder, to one end of which the valve is
rivetted or fixed, the other end being rivetted to the boiler as shewn. On reference
to Figure 4 it will be seen that the spring C is of sufficient width to ensure that
there shall be no lateral motion of the valve; D is an ordinary spring pressing
directly upon the valve, the power of this spring being regulated according to the
pressure at which it is required the valve B should lift. The rise and fall of the
valve being guided simply by the bending of the spring or holder C, there are no

page_text: pins, joints, or moving parts to stick or rust. The shape of the valves may be cir-
cular, as shewn, or of any other desired form, but in general I prefer to make
them oval or oblong because a greater opening for the outlet of steam in proportion
to the area of the valve is thereby obtained, and this remark applies to all the
valves herein-after described.
Figures 5 and 6 represent a valve similar to that shewn in Figures 3 and 4,
except that the valve is oval, and that instead of resting upon a plain seat it rests
upon a raised bearing or flango E.
Figures 7 and 8 represent an arrangement also similar to that shewn in Figures
3 and 4, but with a dead weight F substituted for the spring D; C¹ is an
additional flat spring or arm guiding the rise and fall of the weight F precisely as
the valve is guided by its arm; thus the weights do not require spindles or other
guides liable to arrest their motion.
Figures 9 and 10 represent a valve B of box or chambered form fixed to the end
of a spring or flexible holder C, with the addition of a weighted lever G to press on
the back of the valve. This lover is supported by a flexible arm C³ in a similar
manner to the valve B The inner end of the lever is not attached to any part,
but simply rests or bears against the under side of the flexible arm C', to which the
said lever is rivetted near the outer end, as shewn. I sometimes use a stop over
the inner end of the lever G, as seen at X, Figure 9, either above the flexible
arm C¹, as shown, or below it.
Figures 11 and 12 represent a scries of valves of comparatively small diameter,
which I employ instead of one large valve for the purpose herein-before fully
explained. Each of these valves B is shewn of box or chambered form, and is
carried by a flexible arm C, as herein-before described with reference to Figures
3 and 4 I prefer to weight them progressively, as herein-before stated, so that
they will open one after another, and give a gradual and efficient relief to the
boiler. They do not have separate openings into the boiler but are placed upon a
pipe H, which communicates with the steam space of the boiler, one opening into
the boiler being thus sufficient for all the valves.
The flat springs or flexible holders C, C³, herein-before described with reference
to Figures 3 to 12 may be applied to safety valves other than the box or chambered
valves shewn in the same Figures; and similarly the box or chambered valves may
be combined with any other suitable arrangement for guiding them to or retaining
them on their seats; but I prefer to use the flat springs and the box or chambered
valves in combination, as described and shewn,
I also sometimes use an clastic seat for safety valves of the box or chambered
form; such seat may be made of asbestos, india-rubber, or other elastic substance
which cannot be destroyed by the heat of the steam.
And having now described the nature of my said Invention, and in what manner
the same is to be performed, I declare that I claim as my "Improvements in Safety
Valves."
First. Constructing safety valves in such manner that any increase above the
normal pressure in the boiler acts upon a flexible disc, and thereby opens the valve,
substantially as herein-before described under the first part of this Invention.
Second. Constructing safety valves substantially as herein-before described and
represented in Figure 1 of the annexed Drawings.
Third. Constructing safety valves substantially as herein-before described and
represented in Figure 2 of the annexed Drawings.
Fourth Constructing valves of box or chambered form resting or bearing upon
a plain or flat horizontal seat, substantially as herein-before described and repre-
sented in Figures 3 and 4, 7 and 8, 9 and 10, and 11 and 12, respectively of the
annexed Drawings.
Fifth. Constructing valves of box or chambered form resting upon a flanged or
raised bearing or seat, substantially as herein-before described and represented in
Figures 5 and 6 of the annexed Drawings.

page_text: Sixth. Rivetting or fixing valves to the end of a flat spring or other flexible
holder, arm, or support, substantially as and-for the purpose herein-before described
and represented in Figures 3 to 12 of the annexed Drawings
Seventh. The combination of a box or chambered valve with a flat spring or
other flexible holder, arm, or support, substantially as herein-before described and
represented in Figures 3 to 12 of the annexed Drawings
Eighth. The several arrangements of safety valves herein-before described and
represented respectively in Figures 3 and 4, 5 and 6, 7 and 8, and 9 and 10, of the
annexed Drawings.
Ninth. The employment upon a pipe communicating with the boiler of a series
of comparatively small valves, whether progressively weighted or not, substantially
as and for the purpose herein-before described and represented in Figures 11
and 12 of the annexed Drawings.
Tenth. The combination with a box or chambered valve of an elastic seat, as
herein-before described.
In witness whereof, I, the said Martyn John Roberts, have hereunto set my
hand and seal, this Twenty-fourth day of February, One thousand eight
hundred and seventy-seven
MARTYN J. ROBERTS. (LS).