IMPROVEMENTS IN THE CONSTRUCTION, OF PRESSURE GAUGES
Year: 1877

page_text: LETTERS PATENT to Aaron Bradshaw, of Accrington, in the County of
Lancaster, for the Invention of "IMPROVEMENTS IN THE CONSTRUCTION, OF
PRESSURE GAUGES."
Sealed the 2nd November 1877, and dated the 31st May 1877.
PROVISIONAL SPECIFICATION left by the said Aaron Bradshaw at the
Office of the Commissioners of Patents on the 31st May 1877.
AARON BRADSHAW, of Accrington, in the County of Lancaster..
MENTS IN THE CONSTRUCTION OF PRESSURE GAUGES."
IMPROVÉ
These improvements are intended to obviate the difficulties hitherto experienced
in gauges for recording pressure of aeriform or other fluids.
According to one modification of my Invention, I cause the fluid pressure which
is required to be ascertained or recorded to act between or against the inner sur-
faces of two elastic diaphragms fixed within an enclosed vessel at a short distance
apart from each other. On each external surface of these diaphragms I place a stiff
plate or washer of metal. The respective superficies of these two plates or washers.
are unequal, and I connect the two plates or washers together by ineans of a central,
bolt passing through them and the two diaphragms as well as through the inter-
vening space.
The fluid pressure to be recorded, acting equally on the inner faces of the
diaphragms, causes the diaphragın which has the plate or washer with the larger
superficies to move the diaphragın which has the plate or washer with the smaller
superficies, and this movement I utilize for registering or recording the amount of
the said pressure acting on the diaphragins, either by causing inercury or other
fluid to rise in a glass tube having a suitable scale, or by acting upon a spring with
a pointer moving over an index plate.
To prevent deterioration of the diaphragm through the action of steam, water, or
other fluid, I fill the cavity between the diaphragms with mercury or other suitable

page_text: fluid, and by this means I preserve the diaphragms from oxydating, and keep them
permanently elastic.
According to another modification of my Invention, I cause the fluid pressure
which is required to be ascertained to act direct upon one end of a column of
mercury in a glass tube provided with a graduated scale. The other end of this tube
communicates with a chamber of much larger diameter, provided with an elastic
diaphragm. Against the other side of this diaphragm a stiff plate or washer of
metal is held by means of a strong coiled or other spring, the force of the said spring
being regulated by a set screw. Thus it will be evident that the fluid pressure acts
direct upon one end of the column of mercury, the other end of which transmits the
pressure to the diaphragm and resisting spring, and at the same time this column
acts as the registering column to indicate the pressure. It also protects the face of
the diaphragm from deterioration, and being itself enclosed it is not subject to
oxydation from the action of the atmosphere.
SPECIFICATION in pursuance of the conditions of the Letters Patent filė
by the said Aaron Bradshaw in the Great Seal Patent Office on the 29th
November 1877.
AARON BRADSHAW, of Accrington, in the County of Lancaster.
MENTS IN THE CONSTRUCTION OF PRESSURE GAUGES."
"IMPROVE-
These improvements are intended to obviate the difficulties hitherto experienced
in gauges for recording pressures of aeriform or other fluids.
According to one modification of my Invention, I cause the fluid pressure which is
required to be ascertained or recorded to act between or against the inner surfaces
of two clastic diaphragms fixed within an enclosed vessel at a short distance apart
from each other... On each external surface of these diaphragms I placé a stiff plate
or washer of metal. The respective superficies of these two plates or washers are
unequal, and I connect the two plates or washers together by means of a central
bolt passing through the intervening space.
:
The fluid pressure to be recorded, acting equally. on the inner faces of the
diaphragms, causes the diaphragm which has the plate or washer with the larger
superficies to move the diaphragm which has the plate or washer with the smaller
superficies, and this movement I utilize for registering or recording the amount of
the said pressure acting on the diaphragms, either by causing mercury or other fluid
-to-rise-in a glass. tube having a suitable-scale, or by acting upon a spring with a
-pointer-moving-over-an-index-plate--
To prevent deterioration of the diaphragin through the action of steam, water, or
other Buid, I fill the cavity between the diaphragms with mercury or other suitable
fluid, 'and by this means I preserve the diaphragms from oxydating and keep them
permanently elastic. -
According to another modification of my. Invention, I cause. the fluid pressure
which is required to be ascertained to act direct upon one end of a column of mer-

page_text: cury in a glass tube provided with a graduated scale. The other end of this tube
communicates with a chamber of much larger diameter, provided with an elastic
diaphragm. Against the other side of this diaphragm a stiff plate or washer of
inetal is held by means of a strong coiled or other spring or springs, tlie force of the
said spring being, if required, regulated by a set screw. Thus it will be evident
that the fluid pressure acts direct upon one end of the column of mercury, the other
end of which transmits the pressure to the diaphragm and resisting spring, and at
the same time this column acts as the registering column to indicate the pressure.
It also protects the face of the diaphragun from deterioration, and being itself
enclosed, it is not subject to oxydation from the action of the atmosphere.
In some cases it may be found necessary to employ two registering tubes of
different diameters, the lower ends of which are both open to the diaphragm as in
the case of the single tube.
Such being the nature and object of my said Invention, I will now proceed to
describe more 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 :-
The construction of this spring gauge with the single diaphragm is shown in
elevation at Fig. 1 of the annexed Drawing, and in section at Fig. 2. a, a, is the
shell or external casing of the gauge; b, b, the glass tube containing the column of
mercury; c, c, the graduated scale; and d, d, the tube by which the fluid pressure
is admitted to the top of the column of mercury. The lower end of this column
rests upon an clastic diaphragm e, e, in a chamber f,f, of much larger diameter than
the glass tube b, b. Beneath this diaphragm is the stiff plate or washer g, g, resting
on the coiled spring h, h. This spring may if required be furnished with a set
scrow for regulating the strength or force thereof, as shown by the dotted lines in
Fig. 2.
Figs. 3 and 4 are similar views of the double diaphragm modification above
described, and Fig. 5 is a transverse section thereof.
The same letters of reference are placed upon corresponding parts of the apparatus,
as in the previous Figures, the principal differences being that in this case the fluid
pressure to be registered instead of acting direct upon the indicating column of
mercury, acts between the inner faces of two elastic diaphragms f and f³, the latter
of which has a plate or washer g¹ of larger superficies than the other g, and the two
plates are connected together by a central bolt i, i. The pressure acting between
the two will cause the plate or washer g¹ to recede or move backwards, drawing
the smaller plate or washer g with it, and the former acting direct upon the
mercury in the chamber f, f, will force it up the tube b, b, a greater or less distance,
according to the pressure exerted between the two diaphragms.
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 be understood that I claim as my Invention,―
Firstly. The construction of a pressure gauge wherein the pressure acts between
the inner surfaces of two elastic diaphragms, to the external surfaces of which are
applied plates or discs of different superficial areas, the two plates being connected
together through and between the washers, the consequent displacement of tho
diaphragm and plates acting directly on the registering column of mercury in
a glass tube, or upon a spring with a pointer moving over a suitable index plate
or dial.
Secondly. I claim the construction of a pressure gauge wherein the pressure acta
direct upon the upper surface of the column of mercury in the glass tube, the lower
end of the said column resting ou an elastic diaphragm, against the other side of
which a stiff plate or washer is pressed by a strong coiled or other spring or
springs, the whole being constructed and operating substantially as and for the

page_text: purposes herein-before more particularly set forth and illustrated by the Drawings
annexed.
t
In witness whereof, I, the said Aaron Bradshaw, have hereunto set my
hand and seal, this Twenty-seventh day of November, in the year of
our Lord One thousand eight hundred and seventy-seven.