IMPROVEMENTS IN INSTRUMENTS FOR DETECTING VARIATIONS OF PRESSURE AND TEMPERATURE, AND IN INDEXES CONNECTED WITH THE SAME, SAID IMPROVEMENTS BEING APPLICABLE FOR PHILOSOPHICAL AND MECHANICAL PURPOSES."
Year: 1880

page_text: LETTERS PATENT to George Edward Pritchett, of Bishop's Stortford, in the
County of Herts, for an Invention of "IMPROVEMENTS IN INSTRUMENTS FOR
DETECTING VARIATIONS OF PRESSURE AND TEMPERATURE, AND IN INDEXES
CONNECTED WITH THE SAME, SAID IMPROVEMENTS BEING APPLICABLE FOR
PHILOSOPHICAL AND MECHANICAL PURPOSES."
PROVISIONAL SPECIFICATION left by the said George Edward Pritchett at
the Office of the Commissioners of Patents on the 20th April 1880.
GEORGE EDWARD PRITCHETT, of Bishop's Stortford, in the County of Herts.
"IMPROVEMENTS IN INSTRUMENTS FOR DETECTING VARIATIONS OF PRESSURE
AND TEMPERATURE, AND IN INDEXES CONNECTED WITH THE SAME, SAID IMPROVE-
MENTS BEING APPLICABLE for PhilosoPHICAL AND MECHANICAL PURPOSES."
This Invention mainly consists in so balancing and fixing tubes and bulbs of
glass or of other suitable materials, that when mercury, spirit, gases, fluids, or
other compounds, are inserted into or connected with the same, any variations
in the weight of the atmosphere or of other pressure, and variations of
temperature will so affect the said instruments and their contents that they
will indicate such variatious automatically or otherwise for barometrital,
thermometrical, and laboratory purposes, and other observations. The instruments
will also act as fire alarms and give warnings of increase and decrease of temperature
and of atmospheric pressure, and they may be placed in circuit with electric and
magnetic currents for signalling purposes. Indexes or dials attached to the said
instruments are actuated by the motion, alteration of balance or change of position
of the instruments, and by magnetic or electric currents.
By placing the index hand, which can be of magnetized steel and soft iron, or a
magnetized bar in connection with magnets, the index hand or bar will be held in
position by the magnetic power, and the index is operated by the rising or falling
of the instruments and the index hand or bar aforesaid. This arrangement of
indexing can be applied to other philosophical and mechanical instruments. Power
generated or obtained by displacing the contents and balance of the instruments
aforesaid, may be utilized for various purposes, such as opening and closing
apertures for ventilation, as well as for many other mechanical and useful
purposes.
:

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said George Edward Pritchett in the Great Scal Patent Office on the
20th October 1880.
GEORGE EDWARD PRITCHETT, of Bishop's Stortford, in the County of Herts.
"IMPROVEMENTS IN INSTRUMENTS FOR DETECTING VARIATIONS OF PRESSURE AND
TEMPERATURE, AND IN INDEXES CONNECTED WITH THE SAME, SAID IMPROVEMENTS
BEING APPLICABLE FOR PHILOSOPHICAL AND MECHANICAL PURPOSES."
This Invention consists in so balancing and fixing tubes and bulbs of glass, metal,
or other suitable materials, that when mercury, spirit, gases, fluids or other
compounds are inserted into or connected with the same, any variations in the
weight or density of the atmosphere, gases, liquids, or of other pressure and
variations of temperaturo will so affect the said instruments and their contents
that they will indicate such variations automatically or otherwise for barometrical,
thermometrical, and laboratory purposes, and other observations. The instruments
will also act as fire alarms, and give warnings of increase and decrease of temperature
and of atmospheric pressure, and they may or may not be placed in circuit with
electric and magnetic currents for signalling purposes. Indexes or dials or both are
attached to the said instruments, and are actuated by the motions, alteration of
balance, or changes of positions of the instruments, and by magnetic or electric
currents. By placing the index hand, which can be of steel and soft iron, or a
magnetized bar in connection with magnets or electro-magnetic currents, the index
hand or bar will be held.in position by the magnetic power, and the index is
operated by the rising or falling of the instruments and the index land or bar
aforesaid. This arrangement of indexing can be applied to other philosophical and
mechanical instruments. Power generated or obtained by displacing the contents
and balance of the instruments aforesaid may be utilized for various purposes, such
as opening and closing apertures for ventilation, as well as for many other incchanical
and useful purposes. For the purposes aforesaid, in connection with barometrical
and thermometrical instruments, I use suitable tubes of glass, metal, or other
material bent to the shapes and angles required, as hereinafter described, and as
shewn in the Drawings, or otherwise. For the duplex barometer and thermometer
I form a bulb or bulbs on the main tube, connected with which is a tubular neck
and tap. When the tap is open the instrument acts as a barometer; when it is
closed it acts as a thermometer. When any compounds or fluids are introduced into
the bulbs any changes of their temperature, composition, or chemical or gaseous
nature will actuate the instruments and record the same on the index and dial
hereinafter described. The bulbs aforesaid have tubes or necks attached to them,
in which thermometers may be fixed, these thermometers being excluded from draught
or passing currents of air indicate temperature steadily and accurately, and diatherinic
effects may be ascertained. For barometrical and such like purposes only, the bulbs
and tap may be omitted and a cistern substituted for them. The bulb serves for
chemical tests or observations: The tubes aforesaid are swung and balanced on
knife or scale edges, upon agate or hard bases fixed on suitable stands. I prefer
making the upper portion of the tube flat instead of round, so as to spread the
mercury and lessen the concavity and convexity of the apex of the mercurial or
other column inserted in the tube, but so as to maintain the required vacuum. From
the apex of the tube I suspend on knife or scale edges a shaft carrying dial and
index arrangements before alluded to, which will be kept vertical by gravity, but
such arrangements may be attached either to the upper or lower end of the tube.
To the axis or centre of the tube I attach a silk or other thread, which is attached
to a needle (or bar called the index hand) at one end of the same; the other end of
this needle or bar passes through an eye fixed to the mechanism of the dial hand.

page_text: When the centre of gravity of the barometer tube alters it either dips or ascends,
consequently both the index hand and dial hand fall or rise, and observations can
be made accordingly. By the aforesaid suspension of the index hand great
steadiness of the dial hand is secured. This instrument overcomes the unsteadiness
of a wheel-barometer, as the mercurial column has no float upon it, and is not
interfered with in any way. The dial hand is actuated by the suspended index
hand, having wheels and pinions, interposed as desired, to govern the speed of the
dial hand. The dial and all concomitant parts may be of such size and scale as
required. A bar of magnetized steel is placed at the lower end of the suspended
dial shaft. It is attached by a telescopic rod to light springs set widely apart so as
to prevent buckling or rucking, and it is put in circuit with electric bells or other
appliances. Attached to an arm or lever on the stand or separately is sheeting of
tinned, enamelled, or varnished iron, also put into circuit with an electric bell or
bells, or as aforesaid. At intervals the enamelling or varnishing is removed, leaving
the tinned surface baro or clear, representing lines. When the barometer tube
aforesaid is actuated the magnetized bar as it passes these lines completes electric
circuit and gives alarm of any alteration in pressure by ringing an electric bell.
For example, these instruments placed in a mine with a bell fixed in the manager's
office would ring notice of any change of atmospheric or gaseous pressure or
temperature in the mine and indicate same, as required. At the base of the
barometer tube is attached a chain, the links of which lie upon the stand of the
instrument. The action of the chain is that it counteracts or equalizes the rise of
the mercury, for whereas the mercury causes the upper portion of the tube
to descend, this action raises the links of the attached chain with it, and so by
increasing or diminishing weight, graduates, balances, equalizes descent or move-
inents of the tube. The same equalization may be effected by attaching cones so as
to dip into vessels of mercury, the displacement of which mercury graduates and
equalizes the movements of the barometric tube aforesaid. For the purpose of
opening and closing apertures for ventilation and other purposes, such as green-
house lights, louvres, blinds, and so forth, I attach lines or other connections of
metal or other materials to the said tube, the rising and falling of which will
operate upon them as may be required; as also for closing or opening valves in tubes
and appliances for shutting out or admitting air, as mentioned in my Patent,
No. 1613, April 20, 1880. A disc of tin, enamelled or otherwise, is also fixed to an
arm or lever springing from the stand or separately to which clockwork is attached,
which causes the said metal disc to rotate or to move the metal aforesaid horizontally,
and which disc, drum, or metal is smoked or covered with prepared or sensitized
paper, by which means when the magnetized bar is allowed to be attracted to it,
i.e., the metal, the point of the magnetized bar or pencil connected with it, delineates
a chart of the barometrical and thermometrical changes during such number of
hours as the clock work or other mechanism is set to move the said tin or sheeting.
Another form of instrument I make for thermometrical purposes and fire alarms
is the same in principle, viz., the displacement of the centre of gravity by the move-
ment of the mercury and contents of the instrument, but is adapted for occupying
smaller spaces when compared with the baroneter and duplex instrument above
described. It consists of a tube or other shape hermetically sealed at one end,
placed preferably horizontally, and supported in a cradle or other metal work
having scale or knife edges attached to the cradle forming its support on standards.
A smaller tube is attached to the larger one, and so bent as to hold mercury or
other fluids. When through change of temperature air or spirit expands or
contracts in the larger tube, the contents of the smaller tube shifts its position and
throws over the instrument, which when connected with an electric bell or system
for giving notice will indicate its movement automatically, and will also operate
on indicators, as may be required. One method I adopt for this purpose is to attach
to the cradle of the main tube a rod of graphite or carbon running along its length,
so that as the instrument is thrown over or falls either at maximum or minimum
temperature it presses upon and makes contact with receivers of carbon or metal

page_text: and so closes the electric circuit required, but I do not adhere to this mode of
communication only, as any other mode of switching may be used. The instrument
is adjusted to operate at the degree of temperature required, preferably by rack
and pinion work; the rack is attached to the larger tube, and the pinion to the
cradle; on turning the pinion the rack work forces the tube to the right or left, thus
the instrument can be set as required, and supplied with scales and indexes for the
purpose aforesaid. I also make other shapes which will be actuated in a similar
manner. Also, I make a vertical form of the said instrument adapted for insertion
into liquids; this instrument is actuated in the same way as the horizontal one by
rack and pinion or other shifting mechanism so as to throw it over, and when
joined up with any system for giving alarm or notice, will operate in same manner
as the instruments aforesaid, on increase or decrease of heat. Among uses these
instruments may be put to may be mentioned warning of fire of spontaneous-
combustion, of increase or decrease of atmospheric temperature in houses, hospitals,
greenhouses, mines, manufactories, ovens, gun cotton and other factories, in fact,
wherever any such notice is required.
Having now particularly described and ascertained the object and nature of
the said Invention, and in what manner the same is to be performed or carried
out in practice, I hereby declare that I claim, substantially as hereinbefore set forth
and described, the Invention of "Improvements in Instruments for Detecting
Variations of Pressure and Temperature, and in Indexes Connected with the same,
said Improvements being applicable for Philosophical and Mechanical Purposes,"
and specially the construction of such like instruments in which the rise or fall of
pressure or temperature causes the instrument to rise or fall upon a centre of
balance, and thus to operate an index hand or sound an alarum, or otherwise
actuate an indicator or indicators. Also the arrangement of magnetized bars
acting on iron dises, tinned or sensitized, operating in the manner and for the
purposes above mentioned.
In witness whereof, I, the said George Edward Pritchett, have hereunto set
my hand and seal, this Twentieth day of October, in the year of our Lord
One thousand eight hundred and eighty.