IMPROVEMENTS IN SAFETY-VALVE APPARATUS FOR STEAM BOILERS."
Year: 1880

page_text: LETTERS PATENT to James Dixon Churchill, of Upper Holloway, in the
County of Middlesex, Engineer, for an Invention of "IMPROVEMENTS IN
SAFETY-VALVE APPARATUS FOR STEAM BOILERS."
PROVISIONAL SPECIFICATION left by the said James Dixon Churchill at
the Office of the Commissioners of Patents on the 1st July 1880.
JAMES DIXON CHURCHILL, of Upper Holloway, in the County of Middlesex,
Engineer. "IMPROVEMENTS IN SAFETY-VALVE APPARATUS FOR STEAM BOILERS."
My Invention relates to improvements in safety valve apparatus for steam
boilers, and according thereto so long as the pressure of the steam in the boiler
does not exceed that for which the apparatus is set, and which I will call the
normal pressure, the safety valve is kept against its seat or closed by means of a
piston acted on by steam pressure in a suitable cylinder in connexion with the
boiler; but on the steam in the boiler rising above the normal pressure a suitable
slide or steam valve is operated in such manner that the above-mentioned piston
is relieved from steam pressure, tending to hold the safety valve to its seat or
closed, and that valve is not only allowed to leave its seat, or open, but its opening
is ensured by steam pressure being brought into action at the opposite side of its
piston to that which obtained whilst the normal pressure was not exceeded in the
boiler and the safety valve was consequently being held to its seat or closed. As
the piston moves in its cylinder after the safety-valve has sufficiently left its seat,
or opened, the slide is returned to its normal position, or a second slide or cut off
valve is brought into operation whereby further movement of the said piston is
arrested, and when the steam pressure in the boiler has been sufficiently lowered the
first named slide or steam valve automatically resumes its normal position, thereby
admitting steam again to the proper side of the piston for returning and holding
the safety valve to its seat or closed.
Apparatus may be constructed in various forms to operate on the principle of my
Invention, as above set forth.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by the
said James Dixon Churchill in the Great Seal Patent Office on the 1st January
1881.
JAMES DIXON CHURCHILL, of Upper Holloway, in the County of Middlesex,
Engineer. "IMPROVEMENTS IN SAFETY VALVE APPARATUS FOR STEAM BOILERS."
"
My Invention relates to improvements in safety valve apparatus for steam
boilers, and according thereto, so long as the pressure of the steam in the boiler
does not exceed that for which the apparatus is set, and which I will call the normal
pressure, the safety valve is kept against its scat, or closed, by incuns of a piston
acted on by steam pressure in a suitable cylinder in connection with the boiler
but on the steam pressure in the boiler rising above the normal pressure a suitable
slide or steam valve is operated in such manner that the above mentioned piston is
relieved from steam pressure, tending to hold the safety valve to its seat or closed,
and that valve is not only allowed to leave its seat or open, but its opening is
ensured by steam pressure being brought into action at the opposite side of its
piston to that which obtained, whilst the normal pressure was not exceeded in the
boiler, and the safety valve was consequently being held to its seat or closed. As
the piston moves in its cylinder after the safety valve has sufficiently left its seat,
or opened, and the steam pressure in the boiler has been sufficiently lowered, the
slido is returned to its normal position, or whilst the safety valve is still open a
second slide or cut off valve is brought into operation whereby further movement
of the said piston is arrested, and when the steam pressure in the boiler has been
sufficiently lowered the first-named slide or steam valve automatically resumes its
normal position, thereby admitting steam again to the proper side of tho piston for
returning and holding the safety valve to its seat or closed.
Apparatus may be constructed in various forms to operate on the principle of any
Invention, as above set forth.
Referring to the accompanying Drawings,-
Fig. 1 (Sheet 1) shows in side elevation a safety valve apparatus according to
my Invention.
Fig. 2 is a plan.
Fig. 3 (Sheet 2) is a side view partly in section showing the cylinder and piston
with the spring loading arrangement.
Fig. 4 is an elevation corresponding to Fig. 3.
1 is a cylinder in communication by 2 with the boiler. This cylinder is truly
bored from 3 to 4, the distance corresponding to the depth of its contained piston 5
which is provided with packing rings at 6. This piston is loaded by a spring 7
interposed between the piston and a cross-head 8 adjustable by turning the nuts 9
on the bolts 10. The piston rod 11 passes freely through the crosshead 8, and has
jointed to it at 12 a lever 13, the joint being so made as to allow of the slight
radial movement of the lever. 14 is a pin serving as fulcrum to the lever 13. This
pin is fixed in an arın or lever 15 in a position eccentric to the fulcrum 16 of this
lever (see Fig. 2a). The pivot constituting the fulcrum 16 of the lever 15 is
supported in a bearing piece 17 fixed on the right hand rod 10. The arm 13* of
the lever 13 is connected by a rod 18 to a D-slide in the steam chest 19 of the
cylinder 20. The ports are arranged as follows:-The top one communicates with
the bottom of the interior of the cylinder, the next lower port communicates with
the exhaust, and the third or lowest communicates with the top of the interior of
the cylinder. In Fig. 1 I have supposed the piston in cylinder 20 to be at the
bottom of the cylinder (which is the normal position) with the full boiler pressure
above it, the port communicating with the top of the cylinder being open to the
steam supply, while the port communicating with the bottom of the cylinder is

page_text: open to the exhaust. In this position the safety valve (which is not shewn, but of
which 21 is the lever, and which is jointed at 22 to the piston rod 23) is supposed
to be closed, and the piston 5 in the cylinder 1 is in its lowest position. Assuming
now that the pressure in the boiler rises above the maximum for which the
apparatus has been set by the nuts 9, the piston 5 will be raised in the cylinder 1
against the resistance of the spring 7, thereby tilting the lever 13 on its fulcrum 14,
and moving the slide in the steam chest 19 of cylinder 20. This movement of
the slide will, to begin with, close communication between the port leading to the
boltoin of the cylinder and the exhaust, and also shut off steain from the port
leading to the top of the cylinder; then it will begin to open to the exhaust the
port leading to the top of the cylinder, thereby reducing the pressure on the top of
the piston in the cylinder 20, whereby the safety valve lever is held down, thus
permitting the safety valve to rise by the pressure of the steam against that valve,
while should the safety valve not open, or should the opening thus obtained not
suffice to release the boiler of the excess of pressure the continued downward
movement of the D-valve will admit steam to the bottom of cylinder 20 below the
piston, thereby bringing it into operation for assisting the opening of the safety
valve. As the piston in cylinder 20 rises, it by means of its rod 23 and the arm
or lever 15, raises the fulcrum 14 and lever 13, thereby returning the slide iu
valve chest 19 sufficiently to close the top and bottom ports to both steam and
exhaust, thus retaining the piston in the position. it has assumed in cylinder 20.
When the steam pressure in the boiler is sufficiently lowered the piston 5 in
cylinder 1 returns to its normal position (see Fig. 3) and in so doing operates the
slide in the valve chest 19 so as to partially open the top port to the exhaust and
the bottom port to the steam, thus admitting steam above the piston in cylinder 20
and returning that piston to the bottom of the cylinder, thereby closing the safety
valve. As the piston descends in its cylinder 20 and closes the safety valve the
slide in the steam chest 19 is returned to its normal position by the movement of
the arm or lever 15 carrying the fulcrum pin 14.
Figs. 5 and 6 (Sheet 3) show another arrangement. In this case the cylinder 1
and its piston and piston rod 11, spring 7, and other parts, are arranged horizontally
and at right angles to the piston in cylinder 20. The D-valve in the steam chest 19
is also horizontal and works at right angles to the piston in cylinder 20. The
rod 11 of the piston that works in cylinder 1 (always open to the boiler pressure)
carries a fulcrum pin 25 able to rock or partly rotate, but secured to the arm 15,
which is connected to the piston rod 23 by a connecting rod 26 and an arm 27.
The excentric pin 14 in this case projects from the fulcrum pin 25 and projects
through a slot in the lever 13. This lever works on a pin at 28, and its arm 13*
is jointed to the rod 18 of the slide in steam chest 19. The operation of this
arrangement, will be readily understood from what has been stated with reference
to the preceding arrangement, it being understood that in the present case the
port in valvo chest 19, which is nearest the lover 13, communicates with the bottom
of cylinder 20, the middle port communicates with the exhaust, and the port
furthest from lever 13 communicates with the top of the cylinder, and that as the
piston in cylinder 20 rises, it, through the arm 15, partly rotates the fulcrum pin 25,
thereby altering the position of the eccentric pin 14.
Fig. 7 (Sheet 4) and Fig. 8 (Sheet 5) show another arrangement. In this case
in lieu of the cylinder 1 and piston 5 already described, two flexible discs 30, 31,
(in the present instance shewn as being corrugated), are employed. These discs
are of metal but will not oxidize, for example, German silver. The disc 30 is
loaded by a spring, the load being adjustable by means of a cross head 8 and nuts 9,
as in the previous arrangement, and the two discs are secured together by three
rings 30 which nip the edges of the discs so as to form a steam-tight chamber.
To the disc 30 is secured a rod 11 from which projects laterally a rigid arın 32
connected by a rod 33 to the lever 13, which is supported on an eccentric pin carried
by an arm or lever 15 supported by a standard 34. It is to be understood that
steam from the boiler enters (vid passage 2) between the discs 30 and 31, and when

page_text: the pressure exceeds that for which the apparatus has been set the rod 11 is raised
in opposition to the spring 7, and the apparatus operates in a similar way to that
already described with reference to the arrangements illustrated in Figs. 1 to 4.
In place of a pair of discs, as above described, a single disc may be employed, this
disc being mounted so as to form the flexible side of a chamber, within which the
steam pressure acts; or two or more pairs of discs forming chambers, the interiors of
which communicate, may be used.
Figs. 9, 10, and 11 (Sheet 6), show another arrangement.
In this case the rod 11 is connected to a piston, such, for example, as the piston 5
that works in cylinder 1 in the first described arrangement of apparatus; or the
rod 11 may be connected to a disc as described with reference to Figs. 7 and 8.
The lever 13 is jointed to the rod 11 and has its fulcrum at 13ª. The arm 13*
of this lever is connected by a rod 13b to the main slide 35. The rod 23 of the
piston that works in cylinder 20 is by an arm 23ª and lever 23b having its fulcrum
at 23° connected to the rod 36 of a second slide or cut off valve 37.
Referring now to Fig. 11, which is an enlarged sectional view of the steam
chest 19 with its contained valves and the ports communicating with the respective
ends of cylinder 20 it will be seen that the top port 20 communicates with the
bottom of cylinder 20, the middle port 20b with the exhaust, and the lower port 20°
communicates with the top of cylinder 20. The main slide 35 is traversed by three
passages, videlicet, an inclined passage 35, a passage 35b, and a passage 35°. The
second slide or cut off-valve 37 is a D-shaped valve with a cross-bar 37 and
passage 37b. Now, according to Fig. 11, the bottom of the cylinder 20 is open to
the exhaust, and the steam port 20 leading to the tops of the cylinder is partly
open. This position of the valves is what I call the normal position, that is to say,
it is a position that obtains when the safety valve is closed. Assuming the pressure
in the boiler to rise above that for which the apparatus is set the rod 11 will
ascend, and, through lever 13 and rod 13b will move down the main slide 35 and
close the ports 20 and 20° to exhaust and steam respectively. As the slide 35
moves further downwards the passage 35c will place the port 20c in communication
through the second or cut off slide 37, and passage 35b with the exhaust 20b, thus
relieving the piston in cylinder 20 from the steam pressure that was above it, thus
allowing that piston to be raised by the safety valve lever 21. Should the safety
valve not rise the main slide 35 will descend further so as to bring the inclined
passage 35 opposite the port 20º, and opposite the passage 37b in the second or
cut-off slide 37, thus admitting steam from the steam chest 19 to the lower part of
the cylinder 20, and forcing up the piston 20, and through its rod 23 and the
lever 21 opening the safety valve. As the piston rod 23 rises it will, through the
arm 23, lever 23b, and rod 36, operate the second or cut off slide 37, which in
descending will close the passage 35ª, thus cutting off the steam supply from the
bottom of the cylinder 20. Also the cross bar 37 will close the passage 35º, thus
disconnecting the top of cylinder 20 from the exhaust. In this position of the
valves the piston in cylinder 20 will be brought to rest.
When the steam pressure
11 is no longer held up,
in the boiler has been sufficiently lowered so that the rod
the main slide 35 will have resumed its normal position, and steam thus being
admitted above the piston in cylinder 20 the safety valve will be closed, the
second or cut off slide being returned to its normal position as the said piston
descends.
Having described the nature of my said Invention, and explained in what
manner it is to be or may be performed or carried into practical effect, I wish it
to be understood that what I consider to be novel and original, and therefore
claim as secured to me under the Letters Patent hereinbefore in part recited is,―
1. Controlling the safety valve of a steam boiler by steam pressure acting on a
piston connected to the safety valve and working in a cylinder, the distribution of
steam to which is effected in such manner that so long as the pressure in the
boiler does not exceed the maximum for which the apparatus is set, the steam
pressure against the piston will be on that side, tending to keep the safety valve

page_text: shut; but on the said maximum pressure in the boiler being exceeded steam will
be allowed to escape from that side of the piston against which it has been acting,
thus relieving the safety valve of its load and allowing it to open; and should it
stick or not open sufficiently, steam will be admitted to so act on the piston as to
cause opening of the safety valve (subsequent arrestation of the piston being effected
by the closing of the steam supply and exhaust ports), the amount of movement of
the piston being regulated by the varying pressure of steam in the boiler, and a fall
in that pressure below the maximum for which the apparatus is set, re-admitting
steam to act on such side of the piston as to recloso the safety valve, substantially
as hereinbefore described.
2. In apparatus for controlling a safety valve by the action of steam pressure on
a piston in a cylinder regulating the admission of steam to and its emission from
such cylinder by means of two slides, one operated by an auxiliary piston or its
equivalent open to the boiler, and the other operated by the piston that is connected
to and controls the safety valve, substantially as described.
3. Constructing and arranging apparatus for controlling safety valves by means
of fluid pressure acting on a piston, as herein before described and shewn respectively
in Figs. 1 to 4 inclusive, in Figs. 5 and 6, in Figs. 7 and 8, and in Figs. 9 to 11
inclusive, of the Drawings.
In witness whereof, I, the said James Dixon Churchill, have hereunto set my
hand and seal, this First day of January, in the year of our Lord One
thousand eight hundred and eighty one.
JAMES D. CHURCHILL. (L.S.)