IMPROVEMENTS IN ESCAPE VALVES AND SAFETY VALVES
Year: 1853

page_text: LETTERS PATENT to Joseph Dilworth, of Preston, in the County
of Lancaster, Engineer, for the Invention of IMPROVEMENTS IN
ESCAPE VALVES AND SAFETY VALVES."
Sealed the 16th May 1854, and dated the 1st December 1853.
PROVISIONAL SPECIFICATION left by the said Joseph Dilworth
at the Office of the Commissioners of Patents, with his Petition,
on the 1st December 1853.
I, JOSEPH DILWORTII, of Preston, in the County of Lancaster,
Engineer, do hereby declare the nature of the said Invention for "In-
PROVEMENTS IN ESCAPE VALVES AND SAFETY VALVES" to be as follows:--
This Invention relates to a peculiar arrangement of valve for effecting
the obtaininent of escape equal to the area of the valve itself; this
is accomplished by employing three valves attached to one spindle, the
bottom valve of the three being of a smaller diameter than the other
two, which are of equal size; these two valves act as equilibrium
valves, the steam both ways at once. The bottom valve fits accurately
in a suitable valve-seat formed in the bottom of a short tube, within
which the disc of the valve works steam-tight, like a piston. As the

page_text: pressure within the boiler increases, the spindle with its three valves is
elevated by the force of the steam exerted against the under side of the
lowest or small valve. By the raising of this valve in its short tube,
the other two valves will be opened considerably, and the steam will
escape therefrom. The valve weight is carried by an upright arm fitted
over the fulcrum of the valve, so that when the lever is elevated and
the steam becomes weakened, the weight is thrown over towards
the working centre of the lever, thereby gradually diminishing its action
upon the valve the more-the-lever is elevated.
SPECIFICATION in pursuance of the conditions of the Letters Patent;
filed by the said Joseph Dilworth in the Great Seal Patent Office
on the 25th May 1854.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I,
JOSEPH DILWORTH, of Preston, in the County of Lancaster, Engineer,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the First day of December, in the year
of our Lord One thousand eight hundred and fifty-three, in the seven-
teenth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Joseph Dilworth, Her special
license that I, the said Joseph Dilworth, my executors, adminis-
trators, and assigns, or such others as I, the said Joseph Dilworth,
my executors, administrators, or assigns, should at any time agree
with, and no others, from time to tinic 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 ESCAPE VALVES AND SAFETY VALVES," upon the con-
dition (amongst others) that I, the said Joseph Dilworth, by an
instrument in writing under my hand and scal, 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

page_text: filed in the Great Seal Patent Office within six calendar months next
and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Joseph Dilworth, do hereby
declare the nature of my said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement, reference being had to the accompanying
Drawings, and to the letters and figures marked thereon (that is to say):
My said Invention relates to a peculiar arrangement of valve for
effecting the obtainment of an escape equal to the area of the valve
itself; this is accomplished by employing three valves attached to one
spindle, the bottom valve of the three being of a smaller diameter than
the other two, which are of equal size; these two valves act as
equilibrium valves, the steam passing both ways at once. The bottom
valve fits accurately in a suitable valve-seat, formed in the bottom of a
short tube or cylinder, within which the disc of the valve works, steam-
tight, like a piston. As the pressure within the boiler increases, the
spindle with its three valves is elevated by the force of the steam
exerted against the under side of the lowest or small valve. By the
raising of this valve in its short tube, the other two valves will be con-
siderably opened, and the steam will escape therefrom. The valve
weight may be carried by an upright arm fitted over the fulcrum of
the valve, so that when the lever is elevated and the steam becomes
weakened, the weight is thrown over towards the working centre of the
lever, thereby gradually diminishing its action upon the valve the more
the lever is elevated.
Fig. 1 of the accompanying Sheet of Drawings represents a ver-
tical section of one arrangement of valve, with the weights attached
externally. A and B are two disc valves of equal area attached to the
common stem or spindle C, which is fitted also at its lower extremity
with a third valve D: As the valves A and B are of equal area in the
parts where the pressure of the steam is exerted, they will be balanced
without any tendency to rise or fall, but the under side of the valve D
will always be acted upon by the pressure of the steam, and is held
down by a weight or spring. This latter valve not only rests upon
a conical seat, but works as a piston in the short tube or cylinder E.

page_text: When the pressure of the steam becomes sufficient to raise the valve
D, it will gradually mount to the top of the tube or cylinder E, where
the steam will escape and lessen the pressure on the under side, where-
upon it will rise a very little higher, as in the ordinary safety valve.
But at the same time that the valve D is rising up the cylinder, the
balance valves A and B are rising also, and allowing the steam to
escape by the branch F. By the time the valve D has arrived at the
top of the cylinder, the valves A and B will be full open to the extent
of their area, thereby allowing a free escape to the steam. As the
pressure of the steam upon the valve D becomes weaker by the rapid
escape through the apertures of the valves A and B, the valve D
would probably not rise sufficiently high; to obviate this defect I pro-
pose employing a peculiarly shaped lever for carrying the weights of
the valve. The weight G, which holds down the valve, is placed above
the fulcrum II, on a vertical arm I of the lever J, and is capable of
being adjusted in height by a set screw or other arrangement. By this
arrangement, when the valve D and lever J are elevated, the weight
will be carried or directed over towards the fulcrum II, and con-
sequently the pressure on the valve will gradually decrease in propor-
tion to the decrease of the pressure of the steam, until the pressure is
sufficiently reduced to permit of the descent of the valve D, and
gradual closing of the balance valves A and B. Instead of the weight
shewn on the Drawing, I propose to use a quadrant shaped weight,
either tapering to one end or parallel, as may be found best suited to
adjust the weight on the valve, according to the pressure of the steam.
The upper end of the valve spindle C passes through a stuffing-box K,
in the top of the valve chamber, and is connected by a link I. with the
lever J; the smaller weight M, on the end of this lever, is employed
merely as a balance weight for the lever and valves. This arrange-
ment of lever and weights is not absolutely necessary; it is equally
applicable to valves of the ordinary description.
Figure represents a vertical section of a safety valve, constructed
on entirely the same principle as that described with reference to
Figure 1, but slightly modified in its details.
Figure 3 is a horizontal section of the same along the line
ll,
b.

page_text: Figure 4 is a transverse section along the line c, d; and Figure 5, a
similar section taken at e, f. In this arrangement, in place of two disc
balance valves being employed, a hollow cylinder A, is now attached by
feathers to the stem or valve spindle B, which is weighted at the bottom
inside the boiler, and is guided at the top by a cylindrical guide C, cast.
on the cover of the valve chamber. A conical flange D is formed on
the top of the cylinder A, which fits into the seat E, the lower edge of
the cylinder also rests in a conical seat F. To the bottom of the
spindle B is fitted a disc valve G, which may be smaller than the other
valves; it rests in a conical seat II, and may be made to act as a steam-
tight piston to the short brass tube or cylinder I, in which it slides
freely, being actuated by the pressure of the steam underneath. The
upper end of this cylinder is closed by the cover J, to prevent the
steam which issues from the under edge of the cylindrical valve A
from exerting any pressure upon the top of the disc valve G, and to a
certain extent impeding its rising. K is an outlet for the extra escape
of the steam when the valve G has risen to the top of its cylinder. A
pipe L is fitted to the bottom of the cylinder I, extending downwards
into the body of the boiler, to convey the steam therefrom direct to
the under side of the valve G; the action of this valve is similar to
that of the first arrangement, the cylindrical valve being opened at the
seat F, by the pressure of the steam upon the under side of the disc
valve G, causing the spindle to rise, and the steam will escape both
through the aperture at the seat F, and also upwards through the
cylinder A; when the valve A is closed, the pressure of the surrounding
steam will be equal on all sides, and render it an effectual balance
valve, offering no resistance to the raising of the valve G. In place of
allowing the steam to escape by the aperture at the seat F, this
aperture may be closed, and the steam make its exit up the centre of
the cylinder A only. The cover J, over the cylinder I, together with
the outlet K, may be dispensed with by putting a cover of about the
same size as the valve G over the cylindrical valve, at a distance above
it, to admit of the full escape of the steam. The pressure upwards on
this cover will be equal to the pressure downwards on the valve G, and
thus
preserve the balance. When there is no aperture at F, this cover

page_text: will of course not be used. Or a cover may be fitted to the top of the
cylindrical valve and connected thereto by a helical spring, to assist in
raising it when it is required to allow the steam to escape.
Having now described and particularly ascertained the nature of my
said Invention, and the manner in which the same is or may be used
or carried into effect, I would observe, in conclusion, that I do not
confine or restrict myself to the precise details or arrangements which
I have had occasion to describe or refer to, as many variations may be
made therefrom without deviating from the principles or main features
of my said Invention; but what I consider to be novel and original,
and therefore claim as the Invention secured to me by the hercin-
before in part recited Letters Patent, is,-
First, the general arrangement and construction of safety valves as
herein-before described.
Second, the system or mode of weighting the levers by placing the-
weight above the fulcrum for the purpose herein-before described.
Third, the application and use of an additional valve, working in a
cylinder or tube, for effecting the opening of the escape valve or valves
to the full extent of the area of such valve or valves.
In witness whercof, I, the said Joseph Dilworth, have hereunto
set my hand and seal, the Twenty-second day of May, One
thousand eight hundred and fifty-four.
JOSEPH DILWORTH (L.S.)