IMPROVE- MENTS IN PRESSURE GAUGES
Year: 1872

page_text: LETTERS PATENT to Karl Wenzel Zenger, of Prague, Bohemia, in
the Empire of Austria, at present residing at the Charing Cross
Hotel, in the County of Middlesex, for the Invention of "IMPROVE-
MENTS IN PRESSURE GAUGES."
PROVISIONAL SPECIFICATION left by the said Karl Wenzel Zenger at
the Office of the Commissioners of Patents, with his Petition, on
the 30th August 1872.
I, KARL WENZEL ZENGER, of Prague, Bohemia, in the Empire of
Austria, at present residing at the Charing Cross Hotel, in the County
of Middlesex, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN PRESSURE GAUGES," to be as follows:-
This Invention has for its object improvement in pressure gauges.
For this purpose I cause the steam or other fluid, the pressure of which
the instrument is required to indicate, to act upon the surface of mercury
or other liquid contained in a small reservoir forming part of the pressure
gauge. This reservoir is connected by a capillary passage with a closed

page_text: chamber, into which enter the lower ends of two upright tubes, and they
dip down into the mercury or other liquid which the chamber contains.
The tubes contain air or other permanent gas, and they are connected
together at their upper ends by a narrow passage. As the pressure on
the mercury or other liquid varies the air will be more or less compressed,
and the mercury or liquid will accordingly stand in the pipes at a higher
or lower level. One of the tubes is a parallel glass tube, and the mercury
or other liquid is visible in it. The column of liquid in this tube indi-
cates the corresponding pressure upon a scale in close proximity to the
tube. The object of the second tube, which is of metal, is to allow of a
scale divided into equal parts to be used, or in other words to ensure that
a given increase of pressure shall cause the liquid column in the glass
tube to rise the same distance at whatever height the column may be
standing. To effect this object the second tube is bored out with a taper
bore, and its longer end dips into the mercury or other liquid which may
be employed. The lower or open ends of each of the tubes should only
have small orifices to prevent a rapid change of pressure, causing the
mercury or liquid to be thrown suddenly out of the tubes.
There is a minute orifice closed by a screw plug near the top of the
metal tube, by opening which the instrument can at any time when out
of use be refilled with air.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Karl Wenzel Zenger in the Great Seal Patent Office
on the 28th February 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, KARL:
WENZEL ZENGER, of Prague, Bohemia, in the Empire of Austria, at
present residing at the Charing Cross Hotel, in the County of Middlesex,
send greeting.
WHEREAS Her most Excellent Majesty Queen 'Victoria, by Her
Letters Patent bearing date the Thirtieth day of August, in the year
of our Lord One thousand eight hundred and seventy-two, in the thirty-
sixth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Karl Wenzel Zenger, Her special license, that
I, the said Karl Wenzel Zenger, my executors, administrators, and assigns,

page_text: or such others as I, the said Karl Wenzel Zenger, my executors, adminis-
trators, 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 PRESSURE
GAUGES," upon the condition (amongst others) that I, the said Karl
Wenzel Zenger, my executors, or administrators, by an instrument in
writing under my, or their, or one of their hands and seals, should par-
ticularly 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 Karl Wenzel Zenger, do hereby declare
the nature of the said Invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by
the following statement thereof, that is to say :-
This Invention has for its object improvements in pressure gauges.
For this purpose I cause the steam or other fluid, the pressure of which
the instrument is required to indicate, to act upon the surface of mercury
or other liquid contained in a small reservoir forming part of the pressure
gauge. This reservoir is connected by a capillary passage with a closed
chamber, into which enter the lower ends of two upright tubes, and they
dip down into the mercury or other liquid which the chamber contains.
The tubes contain air or other permanent gas, and they are connected
together at their upper end by a narrow passage. As the pressure on
the mercury or other liquid varies the air will be more or less compressed,
and the mercury or liquid will accordingly stand in the pipes at a higher
or lower level. One of the tubes is a parallel glass tube and the mercury
or other liquid is visible in it. The column of liquid in this tube indicates
the corresponding pressure upon a scale in close proximity to the tube.
The object of the second tube, which is of metal, is to allow of a scale
divided into equal parts to be used or in other words to ensure that a
given increase of pressure shall cause the liquid column in the glass tube
to rise the same distance at whatever height the column may be standing.
To effect this object the second tube is bored out with a taper bore, and
its larger end dips into the mercury or other liquid which may be em-
ployed. The lower or open ends of each of the tubes should only have

page_text: small orifices to prevent a rapid change of pressure, causing the mercury
or liquid to be thrown suddenly out of the tubes.
There is a minute orifice closed by a screw plug near the top of the
metal tube, by opening which the instrument can at any time when out
of use be refilled with air.
In order that my said Invention may be most fully understood and
Figure 1 is a front view, Figure 2 a side view, and Figure 3 a vertical
section of a pressure gauge constructed according to my Invention.
It also serves as a standard to
The graduations upon the scale
end to end. It will be seen that
a, a, is the reservoir for mercury or other liquid, and a' is a connection
with the boiler or vessel containing the steam or fluid, the pressure of
which the instrument is required to indicate; b is a chamber communi.
cating by a capillary passage with the reservoir a; c and d are two tubes
filled with air and entering the chamber 6; they are connected together
at their upper ends. The tube c is of glass and the bore is parallel. The
tube d is of metal and its bore is taper.
support the glass tube c and the scale e.
are, as the Drawing shews, uniform from
the pressure of the steam or other fluid upon the liquid in the reservoir a
will drive a portion of it into the chamber 6 and up the tubes c and d,
and it will appear in the glass tube c. The Figure upon the scale e, on a
level with the top of the column in the tube c, indicates the pressure,
and that it may do so correctly the taper tube d is so proportioned that
if the capacity of the tubes c and d above the level of the liquid be
called 100 units when the liquid in the reservoir a is exposed only to
atmospheric pressure, or say 15 lbs. on the square inch, then when the
column in the tube c indicates upon the scale e 30 lbs. total pressure the
capacity above the liquid in the tubes c and d will be 50 units, and so
again when the total pressure is 60 lbs. the capacity will be 25 units, and
so on.
If mercury be the liquid employed the height of the column should
be taken into account and compensated. The orifices at the lower ends
of the tubes c and d are contracted; f is a plug which is removed occa-

page_text: sionally when there is no pressure upon the instrument to allow the
tubes to refill with air in case there should have been any loss.
For convenience of manufacture and if great accuracy be not required
the tube d may be bored or drilled out in steps in place of in a regular
taper.
What I claim is, the construction of pressure gauges with an indicating
tube c with parallel bore and with a compensating tube d, substantially
as described.
In witness whereof, I, the said Karl Wenzel Zenger, have here-
unto set my hand and seal, this 17th day of February, in
the year of our Lord One thousand eight hundred and seventy-
three.