IMPROVEMENTS IN BALANCED, SAFETY, AND OTHER VALVES
Year: 1877

page_text: LETTERS PATENT to Martyn John Roberts, of the City of Bath, Esquire, for
the Invention of "IMPROVEMENTS IN BALANCED, SAFETY, AND OTHER VALVES."
Sealed the 10th T107ed the
PROVISIONAL SPECIFICATION left by the said Martyn John Roberts at the
Office of the Commissioners of Patents on the 17th December 1877.
MARTYN JOHN ROBERTS, of the City of Bath, Esquire. "IMPROVEMENTS IN
BALANCED, SAFETY, AND OTHER VALVES."
When large disc valves are used under a great pressure of steam or other fluid
the force necessary to keep them closed is very great, and if they have to be opened
by mechanical force, this also must be powerful. In order to avoid this evil balanced
or differential valves have been used. These valves as ordinarily constructed
consist of two disc valves, connected together by a rod or stem, and in such manner
that one valve opens in the same direction as the steam or other fluid issues, and
the other against such direction, therefore the pressure of the steam or fluid which
tends to force open the one valve is counterbalanced, either partly or entirely, by the
pressure on the other valve, and consequently only a small force is necessary either
to keep the valves closed or to open them mechanically. But it has been found in
practice, especially in the case of steam valves, that however tight and perfect the
fit of such valves is upon their seats when cold the heat of the steam expands the
stem which connects the two valves, so that the valves are separated to a greater
distance than before, and one of them ceases to fit closely upon its seat, and a leakage
of steam ensues. If on the other hand the valves are fitted to their scats when hot
the connecting rod shortens as it cools, and either it or some other part of the
apparatus gets broken.
Now the object of one part of my Invention is to overcome this evil, and this
improvement consists, first, in connecting the seats of the two valves together by a
connection of the same length (or as nearly so as possible) and of the same rate of
expansibility under the action of heat as that which connects the two valves
together, and also in placing the connections of the seats and of the valves near to each

page_text: other; consequently any change of temperature that takes place affects both sets of
connections equally, an equal expansion in length ensues, and as the valves and
their seats thus move together a perfect fit between them exists at all temperatures.
In order to allow of the elongation and contraction in the connection of the seats,
and therefore a rise and fall of the seats themselves, I connect them to the valve
casing by a flexible steam-tight joint, which may consist of an india-rubber or
asbestos washer at the joint, or of a flexible wing rivetted to both the seat and the
casing. The connection which I prefer to employ between the valves consists of
four or other suitable number of stems, placed equidistant from the centre of the
valves and as near the periphery as practicable, while the connection between the
seats should consist of a similar number of stems placed as close as practicable to
the valve stems, but midway between the outer and inner peripheries of the seats.
The valves may be of the box or chambered form described in the Specification of
my Patent of 29 August 1876, No. 3405, or otherwise.
The improvements consists, secondly, in constructing a balanced or differential
valve which does not require such correct fitting as the one above described, and is
free from any error caused by change of temperature, one form of which valve is
composed of a vertical metal pipe some inches long, in communication at or near its
upper part with the steam space of the boiler. At the bottom of this pipe is what
I call a bucket, of about 1/8th of an inch less diameter than the pipe, so as to have
freedom of motion within it, and, say, 4 inches deep. At the top of the pipe is an
escape valve, opening upwards and of larger diameter than the bucket. The valve
is loaded in proportion to its greater area, and it is connected to the bucket by a
rod. Between the bucket and the pipe I place an india-rubber tube, of such thick-
ness as to nearly fill the space between them; the top of this rubber tube is fixed
to the top of the bucket, and its bottom to the bottom of the pipe; or a rubber disc
or plate may be substituted for the rubber pipe The metal pipe is filled with
water, which receives the pressure of steam on its upper surface, and communicates
this to the bucket When the pressure of steam upwards upon the valve exceeds
the pressure of water on the bucket downwards, combined with the load on the
valve, the valve opens The water at the bottom of the pipe will remain com-
paratively cool, because water is a bad conductor of heat downwards, and the tem-
perature of, say, 100° Fahrenheit which it attains will not injure the india-rubber.
In order to prevent any injurious accumulation of dirt or other deposit in the
bucket, and thus add to its weight, I sometimes place a tap or valve in the bottom
of the bucket, on opening which the dirt or accumulation is expelled.
Another modification of my Invention is its application to the discharge of water
from steam cylinders and other apparatus, that is to say, I use the form of balanced
valves as herein-before described with a hinged bottom, and attach this by proper
piping to the cylinder or other apparatus from which water is to be discharged, and
the valve which opens is to be weighted by spring or weight in the manner usual
for safety valves; or sometimes instead of placing a weight or spring in the
ordinary manner upon the valve I use (especially for marine engine cylinders) a
lever in which the spring is placed between its fulcrum and the valve, thus obtaining
a freer motion for the valve in lifting.
Another application of my Invention is to "reducing valves," and in this case I
prefer making the valve which opens of the same area as that of the hinged plate or
bucket below in the metal pipe, and whatever back or "reduced
steam pressure
there may be upon the valve which opens I compensate for by an opposing spring
or weighted lever placed in a convenient position upon the apparatus.
Another application of my Invention is for draining off condensed steam in pipes
for heating factories and other purposes in place of the "steam traps" now in use.
The vessel into which the condensed steain falls communicates at its lower part
with my balanced valve, of which the top valve which opens should be of the same
area as the bottom or hinged plate. A lever hinged at one end to the valve casing
is attached to the rod which connects the two valves, and this lever carries a ball or
float in the condensed steam vessel, thus as condensed water collects in this vessel

page_text: the ball rises, the lever opens the top valve, and the steam in the said vessel blows
out the water.
In any of the above modifications or applications the valve with compensating
bars first herein-before described may be substituted for the valve with the hinged
5 plate.
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 17th
Juno 1878.
MARTYN JOHN ROBERTS, of the City of Bath, Esquire.
BALANCED, SAFETY, AND OTHER VALVES."
"IMPROVEMENTS IN
When large disc valves are used under a great pressure of steam or other fluid
the force necessary to keep them closed is very great, and if they have to be opened
by mechanical force, this also must be powerful. In order to avoid this evil
balanced or differential valves have been used. These valves as ordinarily con-
structed consist of two disc valves connected together by a rod or stem, and in such
manner that one valve opens in the same direction as the steam or other fluid issues,
and the other against such direction, therefore the pressure of the steam or fluid
which tends to force open the one valve 18 counterbalanced, either partly or
entirely, by the pressure on the other valve, and consequently only a small force is
necessary either to keep the valves closed or to open them mechanically. But it
has been found in practice, especially in the case of steam valves, that however
tight and perfect the fit of such valves is upon their seats when cold the beat of the
steam expands the stem which connects the two valves so that the valves are
separated to a greater distance than before, and one of them ceases to fit closely
upon its seat, and a leakage of steam ensues. If on the other hand the valves are
fitted to their seats when hot the connecting stem shortens as it cools, and either it
or some other part of the apparatus gets broken.
Now the object of my Invention is to overcome this evil, and the improvements
consist in connecting the seats of the two valves together by a connection of the
same length (or as nearly so as possible), and of the same rate of expansibility under
the action of heat as that which connects the two valves together, and also in
placing the connections of the seats and of the valves near to each other; con-
sequently any change of temperature that takes place affects both sets of connec-
tions equally, an equal expansion in length ensues, and as the valves and their seats
thus move together a perfect fit between them exists at all temperatures.
In order to allow of the elongation and contraction in the connection of the seats,
and therefore a rise and fall of the seats themselves, I connect them to the valve
casing by a flexible steam-tight joint, which may consist of an india-rubber or
asbestos washer at the joint, or of a flexible wing rivetted to both the seat and the
casing. The connection which I prefer to employ between the valves consists of

page_text: four or other suitable number of stems, placed equidistant from the centre of the
valves, and as near the periphery as practicable, while the connection between the
seats should consist of a similar number of stems placed as close as practicable to
the valve stems, but midway between the outer and inner peripheries of the seats.
Figure 1 of the accompanying Drawings is a vertical section, and Figure 2 a hori-
zontal section of a balanced or differential valve, constructed according to my
Invention.
A, B, are the two valves which are of the box or chambered form described in
the Specification of my Patent of 29 August 1876, No. 3405, or they may be of
any other desired form; C, C, C, C, are rods connecting the two valves together;
D, E, are the seats of the two valves A and B respectively; F, F, F, F, are rods
connecting the two seats. These rods are as nearly as possible of the same length
as the rods C, C, and of the same rate of expansibility, and they are placed as near
to the rods C, C, as is practicable with the object already herein-before explained.
The seats D, E, are not fixed to the valve casing G, but are connected therewith by
flexible steam-tight joints, which, as previously mentioned, may consist of an
asbestos or india-rubber washer, as shown at H, H, or of a flexible wing rivetted to
both the seat and the casing. Or instead of both the seats D, E, being thus con-
nected with the casing only one of them may be so connected, the other one being
fixed to the casing in the ordinary manner
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, constructing balanced, safety,
and other valves substantially as herein-before described, and represented in the
annexed Drawings
In witness whereof, I, the said Martyn John Roberts, have hereunto set my
hand and seal, this 14th day of June, One thousand eight hundred and
soventy-eight.
MARTYN J. ROBERTS. (LS.)