IMPROVEMENTS IN STEAM PRESSURE AND VACUUM GUAGES
Year: 1884

page_text: COMPLETE SPECIFICATION.
I ROBERT MARSDEN of Southgate House Eckington in the County of Derby
and of the Tinsley Park Works Attercliffe Sheffield in the County of York Steel
Manufacturer do hereby declare the nature of my Invention for IMPROVEMENTS
IN STEAM PRESSURE AND VACUUM GUAGES and in what manner the same is to
be performed, to be particularly described and ascertained in and by the following
statement:
This Invention has for its object improvements in what are known as steam
pressure and vacuum guages.
In carrying out this Invention I take a piece of metal wrought iron or steel of
the following general form see Fig. 1. A A. and a counterpart of the same as
shewn in Fig. 2 A 1. I then by turning or other means sink in the side of each
a hollow or cavity B B Fig. 3. and I form a narrow ridge C. C. Fig. 3. of such
diameter as may be necessary for the purpose required. I then form a communi-
cation by drilling or otherwise between the inside hollow or concave portions and
the edges or backs of the pieces of metal wrought iron or steel as shewn at Fig. 3
D & D 1. I then take a disc or circular plate of steel E or of such other metal as-
may be found suitable of the requisite thickness according to the pressure the
guage is intended to register and after carefully hardening tempering and if water
is to be used plating or electrotyping and flattening the same screw it very
tightly between the two outer plates A and Al named, above resting it upon the
narrow bearing edges c. c as shewn in Fig. 3. Over the aperture communicating
with the hollow on the front side I place a glass tube F and firmly fix the same
at the bottom end by packing and glaud in the ordinary way and then secure the
same from injury by a netal and glass casing G which is fastened to the front
plate by two screws.
The inside of the glass tube F which is open at the top is preserved from
dust etc. by a little cotton wool or in any other manner that may be thought best
see H. The casing G likewise contains the register or index of pressure at the
back of the glass tube as shewn. To the aperture D in connection with the back
of the disc is connected a pipe I. which may be either screwed into the back plate
or connected by flange or in any other way that will stand the requisite pressure
and may then te attached either to the boiler or such other part of the apparatus
as may be desired.

page_text: When the different parts are all prepared I fill the back and front cavities BB
on each sido of the disc E. either with mercury or coloured water on the front
side till it stands at zero on the index and on the back if with mercury sufficiently
high to prevent any water or steam coming in contact with the disc E and
corroding it.
'
The action of the guage is as follows viz. the steam or water presses through
the pipe I at the back upon the mercury and this pressing upon the disc of steel E
causes it to become slightly concave while the convex side pressing upon the
mercury in the front causes it to rise in the glass tube F in proportion to the
pressure acting upon the back,
To counteract the expansion or. contraction of the mercury by differences of
temperature and where great exactness is required there is placed in the front
plate or in such other part as may be most convenient a regulating screw K which
when forced forward or withdrawn as the case may be will bring the mercury or
water in the glass to zero upon the index but in doing this the pressure on the
back must be taken off and the pipe I at the back open to the atmosphere by
taking out the screw L or unscrewing the union joint.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the saine is to be performed I declare that what
1 claim as my Invention is the use of the disc of steel or other metal connected
in the manner as shewn in the Drawings and which are too plain to need further
description.