IMPROVEMENTS IN APPARATUS FOR PREVENTING THE EXPLOSION OF STEAM BOILERS
Year: 1856

page_text: LETTERS PATENT to John Kershaw, of Stockport, in the County of
Chester, Manager, for the Invention of "IMPROVEMENTS IN APPARATUS
FOR PREVENTING THE EXPLOSION OF STEAM BOILERS."
Sealed the 8th July 1856, and dated the 25th January 1856.
PROVISIONAL SPECIFICATION left by the said John Kershaw at the
Office of the Commissioners of Patents, with his Petition, on the
25th January 1856.
I, JOHN KERSHAW, of Stockport, in the County of Chester, Manager,
do hereby declare the nature of the said Invention for IMPROVEMENTS IN
APPARATUS FOR PREVENTING THE EXPLOSION OF STEAM BOILERS, to be as follows:-
My Invention consists of an improved apparatus for giving notice when the
level of the water in the boiler is too low; this apparatus consists of a compen-
sating, or other valve, to which a rod and float are attached; as long as the level
of the water is not too low, the valve is held closed by the float, but as soon as
the level of the water is too low, the weight of the float overcomes the pressure
of steam against the valve, and the valve is opened, whereby a portion of steam
is allowed to escape, and give notice by means of a steam whistle or otherwise.
I prefer to make the float of hollow metal, and to use a compensating valve,
but the details may be varied.
Another part of my Invention consists in the application of an improved
collapse valve to boilers that are furnished with exploding plates; the object
of this valve is to admit air into the boiler, as soon as the pressure of steam
in the boiler is less than that of the atmosphere. By the application of this
collapse valve the exploding plate will not be injured by the pressure of the
atmosphere thereon, when a partial vacuum is formed in the boiler.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Kershaw in the Great Seal Patent Office on the
25th July 1856.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
KERSHAW, of Stockport, in the County of Chester, Manager, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-fifth day of January, in the year of our Lord
One thousand eight. hundred and fifty-six, in the nineteenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said John Kershaw, Her special license that I, the said John Kershaw, my
executors, administrators, and, assigns, or such others as I, the said John
Kershaw, my executors, administrators, and assigns, should at any time agree
with, and no others, from time to time 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 APPA-
RATUS FOR PREVENTING THE EXPLOSION OF STEAM BOILERS,' upon the condition
(amongst others) that I, the said John Kershaw, my executors or adminis-
trators, by an instrument in writing under my, or their, or one of their hands
and seals, 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 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 John Kershaw, 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 state-
ment, that is to say:―
The nature of my Invention consists in an improved combination of a float
with a valve, and whistle or signal, whereby notice is given when the level of
the water in a steam boiler is too low; also in the application of a collapse
valve to boilers furnished with exploding plates. And in order that my
Invention may be fully understood and readily carried into effect, I will
proceed to describe the means pursued by me, reference being had to the
accompanying Drawing and to the Figures and Letters marked thereon.
Fig. 1 is an elevation of my improved apparatus; a is part of the boiler, to
which is attached by rivets or otherwise the box or casing b; the valve c is
jointed to the upper end of the rod d, and to this rod is attached the float e,.
which may be made of one, two, or more bollow metal balls, according to
i

page_text: AL
circumstances; the seating of the valve c is made at the lower end of the
tube f, screwed above in the box b, and in communication with the whistle g.
I would remark here that a compensating valve may be used, instead of the
one shewn. h is a collapse valve of the usual construction; and i is a plate of
metal, the strength of which is calculated so that it will explode when the
pressure of the steam in the boiler becomes greater than the boiler may with
safety bear; this plate, which is in communication with the atmosphere through
the openings in the lid j, forms no part of my present Invention. The mode
of operation is as follows:-As long as the level of the water in the boiler is
not too low, the valve c is held closed by the float e, but as soon as the level
of the water is too low, the weight of the float e overcomes the pressure of the
steain acting against the under side of the valve c, consequently the valve c
opens, whereby portion of steam is allowed to escape, and rushing up the
tube f, causes the whistle g, to give notice. I wish to remark, the escaping
steam instead of acting on the whistle g, may be otherwise disposed of to give
the required notice. The object of the collapse valve h, as is well understood,
is to admit air to the boiler in case of a partial vacuum being formed therein,
when boilers are provided with exploding plates, such as the one marked i, it
is very important to prevent the action of the air on the upper surface of the
plate. When the pressure within the boiler exceeds the pressure of the
atmosphere, the pressure on the plate i has a tendency to force it outwards,
but as soon as the pressure in the boiler becomes less than that of the atmo-
sphere, the pressure on the upper surface of the plate would, if the collapse
valve were not applied, depress the plate, and these constant actions on opposite
sides of the plate would be very injurious to it.
Having thus described the nature of my Invention, and the manner of
performing the same, I wish to remark that I do not limit myself to the
details herein set forth, but I do claim the improved apparatus shewn and
described, for preventing the explosion of steam boilers, and the application of
a collapse valve in combination with an exploding plate.
In witness whereof, I, the said John Kershaw, have hereunto set my
hand and seal, the Twenty-fourth day of July, in the year of our Lord
One thousand eight hundred and fifty-six.
Witness,
H. B. BARLOW, Manchester.
JOHN KERSHAW. (L.S.)