AN IMPROVED STEAM GAUGE
Year: 1866

page_text: PROVISIONAL SPECIFICATION left by George Davies at the Office of
the Commissioners of Patents, with his Petition, on the 23rd June
1866. A communication from abroad by Emmett Quinn, of Washington,
Columbia, in the United States of America.
I, GEORGE DAVIES, of No. 1, Serle Street, Lincoln's Inn, in the County of
Middlesex, and No. 87, St. Vincent Street, in the City of Glasgow, Civil
Engineer and Patent Agent, do hereby declare the nature of the said Inven-
tion for "AN IMPROVED STEAM GAUGE," (a communication to me from abroad
by Emmett Quinn, of Washington, Columbia, in the United States of
America,) to be as follows:-
It is well known that tubular steam gauges of the ordinary construction
cannot be used with boilers in which the steam is raised to a very high
pressure, inasmuch as the column of mercury in the gauge is not of sufficient
weight to overcome the pressure of the steam which would force it from the
tube.
The object of this Invention is to construct a tubular gauge adapted for
indicating the force of high-pressure steam without using a column of
mercury of more than the usual vertical height. In carrying out this Inven-
tion, two, three, or more vertical tubes (of about the ordinary height used in
tubular pressure gauges) are arranged in juxtaposition, and connected together
alternately at top and bottom by curved or other necks, so as to form in effect
one long zig-zag tube. The necks joining these tubes are each provided with

page_text: a cock, the lower cocks having merely the ordinary transverse passage through
the plug, so as to connect or disconnect the several tubes, whilst the upper
cocks (in addition to the ordinary transverse passages) are provided also with
vertical passages leading from the top of the plug to the vertical tubes; these
passages are ordinarily closed by a cap, which screws on to the top of the
cock, but upon removing this cap and turning the plug into the proper
position the tubes can be charged with mercury or other fluid through these
vertical passages. The first vertical tube of the series is to be placed in con-
nection with the steam space of the boiler, and the last vertical tube is formed
of glass, and is provided with a properly graduated scale or index plate. The
vertical tubes are to be filled with mercury or other dense fluid to about half
their height, and then filled up with water, oil, or other incompressible fluid
of a less specific gravity than that in the lower portions of the tubes;
the cocks are now to be turned so that all the tubes will communicate with
each other, when the instrument will be ready for use. In a gauge of this
description the resistance offered by the mercury to the pressure of the steam
increases in proportion to the number of tubes employed; the mercury
cannot be raised in one tube without forcing the water above it into the next
tube, so as to depress the mercury in this tube, and therefore the movement
of the mercury in each tube will correspond to that in the first, the weight of
each additional column of mercury raised being added to that of the others,
and the pressure indicated being the sum of the weights of all the columns,
so that by the use of a sufficient number of tubes any amount of pressure may
be indicated without danger of the mercury being expelled from the gauge.
By closing the cocks the instrument may be safely transported at any time
without fear of the fluids in one tube becoming mixed with those in the
others. It will be evident that a single tube or pipe bent to a zig-zag form
may be used instead of a series of straight pipes connected by necks, as
herein-before described; the construction and arrangement of the parts may
also be otherwise varied without departing from the main features of the
Invention.