AN IMPROVED CONSTRUCTION OF ELECTRIC CONTACTMAKING THERMOMETER OF ERIC CONTACT MAKING THETER
Year: 1882

page_text: "
LETTERS PATENT to John Formby of Formby near Liverpool in the County
of Lancaster for an invention of AN IMPROVED CONSTRUCTION OF ELECTRIC
CONTACTMAKING THERMOMETER
"
PROVISIONAL SPECIFICATION left by the said John Formby at the Office
of the Commissioners of Patents on the 22nd March 1882.
"
JOHN FORMBY of Formby near Liverpool in the County of Lancaster AN
IMPROVED CONSTRUCTION OF ELECTRIC CONTACT MAKING THERMOMETER"
The object of this Invention is the application and conversion of an ordinary
horizontal Thermometer whether Mercurial or Spirit into an Electric contact
making Thermometer maximum or minimum or both, and the improvements
consists in suspending and supporting the thermometer by a peg through the
medium of a cord connected with a screw or sliding bar secured to the Thermo-
meter which will enable such thermometer in its normal state to assume a
horizontal position, and also allow any variation in the height of the mercury or
spirit column to make or break contact at any required temperature or temperatures
maximum or minimum.
The underside of the thermometer is provided with two metal arches one on
either side the point of suspension and insulated from each other one making
contact at maximum and the other at minimum. One of the ends of each of
these metal arches dip into a mercury cup so that metallic contact is always
maintained whilst the other ends make metallic contact only when required
through the medium of metallic adjustable strips of metal secured to a metal plate
forming the frame to which the terminals are secured. The said terminals are
connected with wires leading to an Electric Battery as usual.
The range between required maximum and minimum temperatures can be
regulated by turning the suspending peg so as to increase or decrease the distance
from the mean point to be moved through by the contact making points.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John Formby in the Great Seal Patent Office on the
22nd September 1882.
JOHN FORMBY of Formby near Liverpool in the County of Lancaster. "AN
IMPROVED CONSTRUCTION OF ELECTRIC CONTACT MAKING THERMOMETER
"
The object of this Invention is the application and conversion of an ordinary
horizontal Thermometer whether Mercurial or Spirit into an Electric contact
making Thermometer maximum or minimum or both and the improvements may
be described as follows:-
On a back board or frame I fix a peg or bar which support rollers made of
cork fitting tightly on the said peg, from these rollers cords or fine metallic wires
depend supporting at their lower ends a cross bar from which a Thermometer is
suspended and which in its normal state assumes a horizontal position, and allows
any variation in the height of the mercury or spirit column to alter its position
so as to make or break electric contact at any required temperature or temperatures
maximum or minimum.
For both maximum and minimum at a convenient position at the end of the
Thermometer farthest from the Bulb two metal fingers are placed and are
insulated from each other one making contact at maximum and the other at
minimum. One of the ends of each of these metal fingers dips into a mercury cup
so that metallic contact is always maintained whilst the other ends make metallic
contact only when required through the medium of metallic adjustable strips of
metal secured to a plate forming the frame to which the terminals are secured the
said terminals are connected with the wires leading to an Electric Battery
The range between the required maximum and minimum temperatures is
regulated by set screws provided for this purpose.
In order that the Invention may be well understood and explained in detail
I have hereunto annexed a Sheet of Drawings made about full size upon which
are marked letters of reference on corresponding parts on all the Figures alike.
DESCRIPTION OF DRAWINGS
Fig. 1. represents in front elevation the general arrangement and combination of
Thermometer and apparatus in connection therewith.
Fig. 2. represents an end view of the same, and
Fig. 3. represents a detached portion or modification of the mercury cups
designed for maximum and minimum working by double circuit.
In these Figs a is the Thermometer carried by the cork slide b supported on the
cross bar c suspended by the fine copper wire threads d from the cork rollers fƒ
fitting stiffly on the rod or peg e secured to the frame n. g. is the scale and
stand fastened to the frame n by a screw which will admit of the said scale being
readily adjusted. To the frame n the recording contact spring his secured the
position of which can be regulated by the adjusting screw k. The wire with
which it is designed to make contact is spirally twisted round the tube of the
Thermometer. One end of this wire is placed in an adjustable position
immediately above the recording contact spring h for maximum and below it for
minimum working, and the other end dips in mercury (so as to make metallic
contact therewith) contained in the cup m. The surface of the spring finger h
where contact is made must by preference be coated with platinum, and the wire
must be insulated up to its contact making points.

page_text: The Thermometer as shewn in the drawing is fitted up for maximum working
only, the arrangement for minimum working being shewn in dots but when
maximum and minimum working is required with two circuits there must be two
mercury cups m and two separate insulated wires wound on the tube of the
Thermometer side by side. When the Thermometer is set for working its
twisted wire is situated immediately above or below the contact making spring h
and as the temperature increases and the mercury rises in the tube of the
Thermometer its end becomes depressed or lowered so as to cause the wire / to
make or break contact as desired with the spring h.
The resistance to breaking of the Electric current causes a slight stick or
adhesion at the point of contact which varies with the Quantity of current. The
battery used therefore should give good Tension but little Quantity. A very
slight stick or adhesion is an advantage inasmuch that it keeps the Thermometer
steady with scarcely any appreciable loss of accuracy. The sticking of the parts
of contact can be controlled in two ways. First by increasing the Resistance in
circuit so long as the current is not reduced till it is too weak to work the
apparatus controlled by the Thermometer and Secondly By thickening the
mercury contact insulation and so increasing its displacement so long as this does
not interfere with make of contact and steadiness under vibration. By utilising
the stick or adhesion more fully steady.maximum and minimum working with
small range may be got with a single circuit. In working it is important that the
recording spring contact finger h is connected to the positive pole x of Battery
and the mercury cup m to the negative pole o. The Thermometer will work the
best if the working Resistance of the Electric circuit is between the negative pole
and the mercury cup m, and if the recording spring contact finger h is connected
to the positive as directly as possible therefore if maximum and minimum working
with two circuits be desired there must be two mercury cups as seen at Fig. 3 of
the drawings, and two complete circuits the two contact wires being insulated
and wound on side by side.
.
When powerful circuits of greater Quantity have to be used a heavier mercury
column will be necessary, but magnetic power can be increased to a very great
extent by increasing the Resistance of the apparatus worked by the Thermometer
and the number of Battery cells arranged in Tension thereby leaving the
Quantity of current passing unchanged and so able to be worked by the same
Thermometer.
Having now described the nature of my said Invention together with the means
I employ for carrying the same into practical effect I wish it to be understood in
conclusion that what I claim as new and as of my Invention is:—
The adaptation and conversion of an ordinary Thermometer into an Electric
Recording Thermometer either maximum or minimum or both in the manner as
herein substantially described setforth and fully illustrated in the drawings
annexed.
In witness whereof, I, the said John Formby have hereunto set my hand
and seal this the Twentieth day of September in the year of Our
Lord One thousand Eight hundred and Eichto two
Witness:-
=
JAMES G GANDY J.C
Hyning
Westmoreland.
JOHN FORMBY (L.S.)