IMPROVEMENTS IN PRESSURE GUAGES
Year: 1864

page_text: PROVISIONAL SPECIFICATION left by William Weild at the Office
of the Commissioners of Patents, with his Petition, on the 13th July
-
1864. Partly a communication from abroad by Philip Justice, of
Philadelphia, in the United States.
I, WILLIAM WEILD, of the City of Manchester, in the County of Lancaster,
Consulting Engineer, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN PRESSURE GUAGES," the result partly of my own Invention,
and partly of a communication from abroad made to me by Philip Justice, of
Philadelphia, United States, to be as follows:-
The Invention relates to guages upon the principle of those which are
arranged so that the pressure to be measured or guaged will act upon a
piston of small area, the motion of which is transmitted to a piston of larger
area (or vice versa). The second piston acting against the pressure of any
suitable fluid such as mercury, which is so arranged as to rise into and fill a
tube higher and higher the further the pistons are moved, so that a column of
this fluid is obtained of greater height and consequently of greater pressure for
every increase in the extent of the movement in the pistons, the height of such
column indicating the pressure acting upon the pistons.
The first part of the Invention consists of an improved combination, arrange-
ment, and construction of pressure guages, acting upon the above principle
as follows: If the pressure of steam is to be guaged, an inverted syphon or
bent pipe connection is made between the steam and the guage so that a
quantity of condensed steam will collect in the bend of the pipe, which will
prevent the hot steam from coming in direct contact with the diaphragm of

page_text: the guage. The diaphragm acted upon by the pressure of the medium is a
disc of prepared vulcanised india-rubber which is placed with its outer edge
against a seating in the lower part of the guage and is secured against this
seating to make a tight joint by a perforated screw plug which acts upon that
part of the diaphragm against the seating, but leaves the central portion of the
diaphragm exposed to the action of the pressure to be guaged: A piston or plug
comes against the diaphragm upon the side opposite to that upon which the
pressure acts, so that the pressure in fact comes directly upon the end of the
piston, the diaphragm being employed merely to prevent the escape of fluid
past the piston, which can thus be made to fit freely without the necessity for
packing. The piston above named is connected with another piston, the end
of which acts against another elastic diaphragm of prepared india-rubber,
which is kept against a seating by a disc which presses upon the margin of
the diaphragm so that the mercury placed in the cavity between the diaphragm
and disc cannot escape. The disc is pressed down upon the diaphragm by a
part at the lower end of a vertical metallic tube (open at one side) which
forms a cover for the glass tube into which the mercury rises when the
pistons are acted upon, the vertical metallic tube being graduated so as to
measure the height to which the column rises in the glass tube. The lower
end of the glass tube is made conical, so as to enter and expand a short elastic
tube of prepared india-rubber against the sides of a hole in the central part
of the disc of the diaphragm, which acts upon the mercury so as to make a
tight joint with the lower part of the glass tube and prevent the escape of
mercury. The glass tube is held down in its place by a screw at the upper part
of the metallic tube, and this screw is so arranged that the upper end of the
tube is open to the atmosphere. The glass tube may be made with a circular
bore, but to render the mercury plainly visible, while at the same time
keeping it small in capacity, the bore is made of a flat or oval shape and the
tube is set with the broad part of the bore so as to be towards the eye when
observing the height of the column. To check oscilliations in the column of
mercury a valve of prepared india-rubber or other suitable elastic material is
placed in the bottom of the central hole of the disc in which the lower end of
the glass tube is inserted. This valve consists of a disc with two slits cut at a
right angle to each other, or a piece of sponge or other porous material may
be substituted.
The second part of the Invention consists in modifications of pressure
guages, upon the principle of those herein-before described, which will enable
them to be employed for ascertaining maximum pressures as a check upon
engineers and stokers, and consists in placing a valve between the disc which

page_text: is in contact with the mercury and the lower end of the glass tube, this
valve allowing the mercury to ascend but preventing its descent till the valve
is lifted or moved to allow the mercury to pass down.
This part of the Invention is carried into effect by placing a small flat
valve in a hollow in a common plug tap having two ways through it, one
covered with a valve, the other uncovered, so that when the plug tap is
turned in one position mercury can ascend through the valve but cannot
descend, and when in the other position it can both ascend and descend.
Another method of carrying this part of the Invention into effect is by
fixing a lever valve for the mercury to pass through, and in opening the valve
by pressing upon one end of the lever of the valve by a rod passing down the
interior of the glass tube.