IMPROVEMENTS IN THE CONSTRUCTION OF PRESSURE AND VACUUM GAUGES
Year: 1857

page_text: LETTERS PATENT to John Parkinson, of the Victoria Works, Bury, in
the County of Lancaster, Engineer, for the Invention of "IMPROVEMENTS
IN THE CONSTRUCTION OF PRESSURE AND VACUUM GAUGES."
Sealed the 22nd January 1858, and dated the 14th August 1857.
PROVISIONAL SPECIFICATION left by the said John Parkinson at the
Office of the Commissioners of Patents, with his Petition, on the
14th August 1857.
I, JOHN PARKINSON, of the Victoria Works, Bury, in the County of Lan-
caster, Engineer, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN THE CONSTRUCTION OF PRESSURE AND VACUUM GAUGES," to be
as follows:-
In the differential pressure gauges of the usual construction a column of
mercury is forced from a glass tube into an iron tube, or the reverse, and the
accuracy of the gauge depends upon the relative proportions of the diameters
of the two tubes. In gauges of the present construction the internal surface
of the iron tube is liable to oxidation, which in the course of time reduces its
area, thereby causing the indications of the pressure to be incorrect. Now,
in order to remedy this defect, I make the tube into which the mercury rises
of gutta percha or other material that is not liable to oxidation, and is not
acted upon by the mercury; by this means the relative proportion in the

page_text: diameters of the tubes remains at all times the same, and the indications of
the pressure remain true. I prefer to enclose the gutta percha tube in a
metal one to protect it from injury. The above improvements are applicable
to vacuum gauges.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Parkinson in the Great Seal Patent Office on the
13th February 1858.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
PARKINSON, of the Victoria Works, Bury, in the County of Lancaster, Engi-
neer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fourteenth day of August, in the year of our Lord
One thousand eight hundred and fifty-seven, in the twenty-first year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said John Parkinson, Her special licence that I, the said John Parkinson,
my executors, administrators, and assigns, or such others as I, the said
John Parkinson, my executors, administrators, 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 THE
CONSTRUCTION OF PRESSURE AND VACUUM GAUGES," upon the condition (amongst
others) that I, the said John Parkinson, my executors or administrators, by
an instrumeut in writing under my, or their, or one of their hands and seals,
should particularly 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 John Parkinson, do hereby declare the
nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement (that is to say) :-
In the differential pressure gauges of the usual construction a column of
mercury is forced from a glass tube into an iron tube, or the reverse, and the
accuracy of the guage depends upon the relative porportions of the diameters
of the two tubes. In gauges of the present construction the internal surface

page_text: of the iron tube is liable to oxidation, which in the course of time reduces its
area, thereby causing the indications of the pressure to be incorrect. Now,
in order to remedy this defect, I make the tube into which the mercury rises
of gutta percha or other material that is not liable to oxidation, and is not
acted upon by the mercury; by this means the relative proportion of the
diameters of the tubes remains at all times the same, and the indications of
the pressure remain true. I prefer to enclose the gutta percha tube in a
metal one to protect it from injury. The above improvements are applicable
to vacuum gauges.
And in order that my Invention may be fully understood and readily carried
into effect, I will proceed to describe the means pursued by me, reference
being had to the accompanying Sheet of Drawings, and to the figures and
letters marked thereon.
b
Fig. 1 is a front elevation of a pressure gauge, to which my improvements
are applied; and Fig. 2 is a section of the same. a is the glass tube attached
to the plate 6 by the upper flange c and lower flange d, in the usual manner;
e is a pipe in communication with the steam or other fluid, the pressure of
which acting on the column of mercury in the tube a, forces the said mercury
into the gutta percha tube f. This tube is enclosed in the metal tube g to
protect the gutta percha. The lower end of the tube g is secured to the lower
part of the plate b by the flange d, and the upper end of the tube g is fur-
nished with a top h, through which is a hole to admit air to the tube ƒ as
usual.
In pressure gauges of the usual construction, in which steam acts on a
column of mercury and forces it into an iron tube, it is found after the gauge
has been in use for a short time that water accumulates above the mercury
in the iron tube; consequently, when the mercury rises in the glass tube it
descends in the iron tube, and the water descending with the mercury wets
the internal surface of the said iron tube and causes it to corrode or rust; by
this means the internal area thereof is diminished and the accuracy of the
gauge is destroyed. But when the tube f is made of gutta percha or any
other suitable incorrodible material, it is evident that no variation can occur
in the accuracy of the pressure indicated.
My improvements in the construction of vacuum gauges consists in making
the syphon connected with the condensor of gutta percha or other suitable
incorrodible material, and will be readily understood without illustrative
Drawings.
Having thus stated the nature of my Invention, and described the manner
of carrying the same into practical operation I wish to observe that I do not

page_text: limit myself to the details given, as the same may be modified; but what I
claim is, the application of gutta percha or other suitable incorrodible material
to the tubes of pressure and vacuum gauges, in the manner and for the purposes
described.
In witness whereof, I, the said John Parkinson, have hereunto set my
hand and seal, this Twelfth day of February, in the year of our Lord
One thousand eight hundred and fifty-eight.
Witness,
H. B. BARLOW,
Manchester.
JOHN PARKINSON. (L.S.)