AN IMPROVED SAFETY VALVE, FOR STEAM BOILERS
Year: 1884

page_text: We JEREMIAH PENDLEBURY 25 Park Road Preston, Engineer and RICHARD
PENDLEBURY 20 Schleswig Street Preston, Engineer do hereby declare the nature
of our invention for AN IMPROVED SAFETY VALVE, FOR STEAM BOILERS to be as
follows:-
The invention consists principaly of two parts, the first being a small valve about
of an inch diameter, and the second being a cylinder fitted with a piston and rod,
(the size of the cylinder if applied to a 3 inch safety valve would be about 1 inches
diameter and 3 inches long) This valve and cylinder are connected, and a passage
leads from the box containing the valve to the lower part of the cylinder beneath
the piston. The piston rod passes through the cylinder cover (which acts as a
guide) projecting a little beyond.
The duty of this apparatus is to relieve the existing safety valve of its load at the
time when the pressure within the boiler is greater than the pressure which the
safety valve is loaded to resist, thereby allowing the safety valve to open to its full
extent, and giving the greatest possible discharge of steam.
The apparatus may be applied to an ordinary safety valve by placing the centre
of the cylinder directly under the lever, in a position between the safety valve and
the weight, the cylinder standing upon a bracket or other support, and having the
top end of the piston rod just clear of the under side of the safety valve lever,
when the safety valve is down upon its seat.
The action is the following. The under side of the small valve is in free
communication with the steam within the boiler. This valve may be held down
upon its seat by means of a dead weight acting directly upon the valve, or by a
lever and weight, or by a spring.
When the pressure within the boiler is increased above the pressure which the
safety valve is weighted to resist, the small valve opens and allows the steam to
pass into the cylinder, the effect of which is to force the piston up, by this means
the top of the piston rod is brought in contact with the under side of the safety
valve lever thereby raising the lever and weight together, thus relieving the safety
valve of its load. When the pressure has been reduced sufficiently the small valve
closes, this is effected by making the valve spindle the same or nearly the same
diameter as the valve seat thus preventing an excess of pressure on the top side,
the weight or spring closing the valve as the pressure is reduced, when the valve is

page_text: closed the pressure is cut off from the underside of the piston (any steam remaining
below the piston will make its escape through a small pipe having a tap which may
be adjusted to allow the surplus steam to escape, and remain in that position) the
piston then descends, and with it the lever and weight of the safety valve.
The supplementary valve and cylinder may be placed in any convenient position
for relieving the ordinary safety valve of its load, as in the case of a safety valve
without a lever, the cylinder might be inverted and placed directly over the safety
valve.
The diameter and length of the cylinder will vary according to the position it
is placed in, it will also vary with the diameter of the safety valve to be relieved.
JEREMIAH PENDLEBURY.
· RICHARD PENDLEBURY.

page_text: COMPLETE SPECIFICATION.
We JEREMIAH PENDLEBURY 25 Park Road Preston, Engineer & RICHARD
PENDLEBURY 20 Schleswig Street Preston Engineer do hereby declare the nature
of our invention for AN IMPROVED SAFETY VALVE FOR STEAM BOILERS and in
what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
The invention consists principally of two parts, the first being a small valve and
the second being a cylinder fitted with a piston and rod. The dimensions of this
valve. and cylinder may vary so as to suit the size of the Safety Valve to be
operated upon. This valve aud cylinder are connected, and a passage leads from
the box containing the valve to the lower part of the cylinder beneath the piston.
The piston rod passes through the cylinder cover (which acts as a guide) projecting
a little beyond. .
The duty of this apparatus is to relieve the existing safety valve of its load at
the time when the pressure within the boiler is greater than the pressure which the
safety valve is loaded to resist, thereby allowing the safety valve to open to its full
extent and giving the greatest possible discharge of steam.
The apparatus may be applied to an ordinary safety valve by placing the centre
of the cylinder directly under the lever, in a position between the safety valve and
the weight, the cylinder standing upon a bracket or other suitable support, and
having the 'top end of the piston rod just clear of the under side of the safety valve
lever when the safety valve is down upon its seat.
The action is as follows. The under side of the small valve is in free*
communication with the steam within the boiler. This valve may be held down
upon its seat by means of a dead weight acting directly upon the valve, or by a
lever and weight, or by a spring.
When the pressure within the boiler is increased above the pressure which the
safety valve is weighted to resist, the small valve opens and allows the steam to
pass into the cylinder, the effect of which is to force the piston up, by this means
the top of the piston rod is brought into contact with the under side of the safety
valve lever, thereby raising the lever and weight together, and thus relieving the
safety valve of its load. When the pressure has been reduced sufficiently, the small
valve closes; this is effected by making the valve spindle, or the upper portion of
the valve, of the same, or nearly the same diameter as the valve seat, thus preventing
an excess of pressure upon the top side, the weight or spring closing the valve as
the pressure is reduced."
When the valve is closed the pressure is cut off from the underside of the piston;
(any steam remaining below the piston will make its escape through a small pipe,
having a tap, which may be adjusted to allow the surplus steam to escape, and
remain in that position) the piston then descends & with it the lever and weight of
the safety valve.
The supplementary valve, and cylinder may be placed in any convenient position
for relieving the ordinary safety valve of its load, as in the case of a safety valve,

page_text: without a lever, the cylinder might be imverted, and placed directly over the
safety valve.
In the accompanying Drawings:-
Figure 1 is a view of an ordinary 3 inch lever safety valve, drawn one half full
size; the full lines shew the valve, the lever, and the weight in their proper positions,
when the valve is closed, or down upon its seat. The dotted lines shew the position
of the valve, lever and weight, when the valve is fully open.
Figure 2. is a section of the cylinder, drawn one half full size, shewing the piston
in two positions, one drawn in full lines, when the piston is at the bottom of the
cylinder, and no steam beneath it, the other drawn in dotted lines and at the top of
the cylinder, the space beneath the piston being full of steam and the upper end of
the piston rod operating upon the safety valve lever as shewn in Figure 1.
Figure 3 is a section of the box containing the valve for admitting and shutting
off steam from the cylinder, together with the valve and its load, drawn one half
full size.
This box and valve are fixed to the upper portion of the boiler, (the boiler plate
being shewn in section and marked B), the weight or load W in this case being
inside the boiler.
The underside of the valve marked A is therefore subjected to the pressure
within the boiler, while the upper side C (which is equal, or nearly equal in area
to A) is subjected to the pressure of the atmosphere, for this reason then, the valve
when open is in equilibrium, and there is no force tending to close it, except the
weight W, which this does when the pressure is sufficiently reduced.
The valve in the drawing is shewn closed but the direction of the steam when
the valve is open, is indicated by the arrows.
Figure 4 is a sectional view of the valve, and box, when the valve is held down
by a spring, in place of a weight as in Figure 3.
The principle of the valve being the same in both cases, that is the lower
surface A in each, being subjected to the pressure within the boiler, and the upper
surface C to that of the atmosphere. This arrangement of the valve is intended to
be applied in cases where a weight is not applicable.
•
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that what
we claim is
:
First, The use of a cylinder and piston for the purpose of opening a safety valve,
or relieving it of its load, and which operates to effect a free discharge of steam
from the boiler, as above set forth.
Second, A valve made on the principle illustrated on the accompanying drawings,
for admitting and shutting off steam from the aforesaid cylinder.
10
1
1007
JEREMIAH PENDLEBURY.
RICHARD PENDLEBURY.