IMPROVEMENTS IN THE CONSTRUCTION OF SAFETY-VALVES FOR DOMESTIC BOILERS AND HOT-WATER APPARATUS."
Year: 1881

page_text: LETTERS PATENT to Christopher Shields, of Manchester, in the County of
Lancaster, for an Invention of "IMPROVEMENTS IN THE CONSTRUCTION OF
SAFETY-VALVES FOR DOMESTIC BOILERS AND HOT-WATER APPARATUS."
PROVISIONAL SPECIFICATION left by the said Christopher Shields at the
Office of the Commissioners of Patents on the 10th October 1881.
"IMPROVE-
CHRISTOPHER SHIELDS, of Manchester, in the County of Lancaster.
MENTS IN THE CONSTRUCTION OF SAFETY VALVES FOR DOMESTIC BOILERS AND
HOT WATER APPARATUS."
This Invention relates to the construction of a valve intended principally to be
applied to domestic boilers and other hot water apparatus for the prevention of
accidents by explosion or collapse, the same valve acting also for the emission of
air during the filling of the boiler or hot water pipes with water.
The body or casing of the valve is made (by preference) of a globular form in
two halves screwed together at the centre. Inside this is a thin hollow copper
ball provided at its upper side with a small valve and spindle working against a
valve seating made in the lower side of a spring piston working in a tubular neck
forming part of the upper half of the valve casing. When the water in the boiler
or the pipes is below the level of the safety valve the hollow ball falls and opens
the small valve for the escape of the air or steam from the pipes or boiler, but as
soon as the water commences to rise inside the globular casing it raises the hollow
ball and causes it to close the small internal valve in the lower side of the piston.
Should the pressure of the water however exceed the resistance of the spring the
piston itself will be raised, and passing above lateral openings made in the neck it
will allow the water to escape.
In the event of cold water being introduced when the boiler or pipe is full of
steam, the partial vacuum formed will cause the valve to open and thus prevent a
collapse.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Christopher Shields in the Great Seal Patent Office on the
6th April 1882.
CHRISTOPHER SHIELDS, of Manchester, in the County of Lancaster.
"IMPROVE-
MENTS IN THE CONSTRUCTION OF SAFETY VALVES FOR DOMESTIC BOILERS AND
HOT WATER APPARATUS."
This Invention relates to the construction of a valve intended principally to bo
applied to domestic boilers and other hot water apparatus for the provention of
accidents by explosion or collapse, the same valve acting also for the emission of
air during the filling of the boiler or hot water pipe with water without the use of
air pipes.
Such being the nature and object of my said Invention, I will now proceed to
describe in detail the manner in which the same is to be or may be performed
or carried into practical effect; and in order that the same may be clearly
understood I have annexed hereunto a Sheet of Drawings illustrative thereof,
and have marked the same with figures and letters of reference corresponding with
those in the following explanation thereof.
Fig. 1 in the annexed Drawing is an external elevation of my improved safety
valve, and Fig. 2 is a vertical section of the same.
The body or casing a, a, of the valve is made (by preference) of a globular form
in two halves screwed together at the centre at b, b. Inside this is a thin hollow
copper ball c, c, provided at its upper side with a small valve d, d, and spindle e, e,
working against a valve seating made in the lower side of a spring piston or
plunger ff, working in a tubular neck a', a', forming part of the upper half of tho
valve or casing.
When the water in the boiler or the pipo is below the level of the safety valve
in the absence of a pressure of steam the hollow ball c, c, remains in its lowest
position, and the small valve d, d, remains open for the escape of the air or steam
from the pipes or boiler; but as soon as the water commences to rise insido the
globular casing a, a, it raises the hollow ball c, c, and causes it to close the small
internal valve d, d, in the lower side of the piston or plunger f, f, as shown at
Fig. 2 in the Drawing.
Should the pressure of the water or steam however exceed the resistance of the
spring g, g, the piston f, f, itself will be raised, and passing above the lateral
opening h, h, made in the neck a¹ it will allow the water or steam to escape.
In the event of cold water being introduced when the boiler or pipe is full of
steam, the partial vacuum formed will cause the valve c, d, to open and thus
prevent a collapse. i, i, is a screwed bush to keep the spring g, g, in its place and
to increase or diminish the pressure, and which may be graduated so as to show the
pressure accurately; h, k, is a cap or cover, which in some cases may be dispensed
with.
On removing this cap and applying pressure to the end of the spindle e, c, the
presence of steam, air, or water in the pipes can be at any time tested.
Having now described the nature and object of my said Invention, together
with the manner in which the same is to be or may be performed or carried into
practical effect, I wish it to be understood that I claim as my Invention, the
peculiar construction of safety valves for domestic boilors and other hot water
apparatus, as hereinbefore described and illustrated by the Drawings annexed, for
1

page_text: the prevention of accidents by explosion and collapse, the same valve also acting
for the emission of air during the filling of the boiler or hot water pipes with
water.
In witness whereof, I, the said Christopher Shields, have hereunto set my
hand and seal, this Fifth day of April, in the year of our Lord One
thousand eight hundred and eighty two.
CHRISTOPHER SHIELDS. (L.S.)