IMPROVEMENTS IN METALLIC THERMOMETERS WITH DIALS
Year: 1885

page_text: WILLIAM HENRY GAUNTLETT of Middlesbro on Tees in the County of York
Engineer do hereby declare the nature of the said invention for IMPROVEMENTS
IN METALLIC THERMOMETERS WITH DIALS to be as follows:-
A plate of sheet Iron eighteen inches square form the dial plate, the front side is
enamel'd, to the back is fixed the working parts, which is formed of two circles,
nearly complete, of brass and Iron, each inch dia, solderd together, this then
form one circle or ring about eleven inches in diameter, with an opening of say one
inch at top, brass being the inner portion, Iron the outside, this ring give the
motive power, by expansion and contraction, to one side of this opening is fixed a
small bracket projecting inwards towards centre of ring, carring two racks, formed
of fine threaded screws about 2 inch apart in plan, and at right angles to a
perpendicular line drawn thro centre of opening and centre of ring, to the other
side of opening, is attach'd one rack or screw, so made with spring, as to press
lightly on a peice of pinion wire, same pitch, as screws, this pinion form the axis,
(which pass thourgh centre of dial plate,) on which the pointer is fixed, the axis,
riding, and revolving, freely, on the two lower racks, while the single rack above
and between the two lower ones, in plan, press gently on the top side of axis, thus
given free motion to pointer, with the least possiable friction, there being no journals,
or centers, the only points of contact, is the two racks, below, and the one above,
with pinion. The bottom part of ring, is securely fixed, to one angle of dial plate,
by means of screws, so as only to grip, a narrow portion and leave each side equal,
and free for action. The bracket carring the two racks, projecting inwards, is
carried to the desired distance, so as to give the proper travel, to corrospond with
degrees on dial. The axis is carried some distance thro pointer, so as to nearly
touch the glass of Frame or case, while the other end is protected, by a small
bracket, fixed to dial plate, presenting a plain surface, so as nearly to touch
the end of axis. On the enamel is a circle, of twelve inches dia, divided into
120 degress, Fahrenheit, 60° being at top, 0 or Zero at bottom.
The dial plate is placed in a sutiable frame, or mounted, in any way, to be hung
on a wall, as in the case of an ordinary Clock.

page_text: Improvements in metallic Thermometers with Dials.
I, WILLIAM HENRY GAUNTLETT, of Middlesbrough-on-Tees, in the County of
York, Engineer, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:-
In a metallic thermometer according to this invention the axis which carries the
index is not supported in fixed bearings, but is held between two or more pieces
which experience a change of position as the thermometric portion of the instru-
*ment responds to variations of temperature. These picces receive equal and
opposite motions, and one or more of them is, or are, applied to the axis at each
end of a diameter.
The effect of the motions of the pieces is to cause the axis to rotate about its
centre line just as if it were carried in fixed bearings; at the same time the friction
is exceedingly small, as there is no sliding contact; consequently the thermometer
is very delicate, and responds readily to small increments and decrements of
temperature.
According to one arrangement a plate of suitable material, such as sheet iron,
forms the dial plate, and on the front side is graduated in degrees. To the back
are fixed the working parts including the device which suffers a change of shape or
volume according to the temperature. This is conveniently formed of two nearly
complete circles of metals, such as brass and iron, having different coefficients of
expansion. These circles are soldered together and form an imperfect ring with
an opening in it. As is well understood this opening will increase and diminish
with changes of temperature.
The ring is held at a point opposite to the opening, and there is fixed to it at
one side of this opening a small bracket projecting inwards towards the centre of
the ring. This bracket carries two racks which may be formed of fine threaded
screws placed at a little distance apart and in a plane parallel to the axis of the ring.
At the other side of the opening there is attached a similar rack or screw connected
to the ring by an elastic bracket. The axis of the index is supported between the
two sets of racks or screws, and is formed of a piece of pinion wire. The axis rides
and revolves or rolls freely on the two lower racks, while the single rack above
which is situated symmetrically with regard to the two lower, presses gently on
the top side of the axis. The motion may thus be described as a rolling one
without the axis of the pinion being at all shifted, because the ends of the ring are
always moving in contrary directions with respect to each other. The axis more-
over is always kept steadily parallel, in consequence of its pinion resting on two
racks as points of support, and the result is that it requires no bush, journal, or
other support. The axis is in fact entirely free from friction except that to which
it is necessarily subject from the action of the racks and pinion. The axis is
carried some distance through the pointer, so as to nearly touch the glass of the
frame, or case, while the other end is protected, by a small bracket, fixed to dial
plate, and thus end wise motion is prevented. On the enamel is a circle divided into
120 degrees, 60° being at the top, 0 or zero at the bottom.

page_text: The dial plate is placed in a suitable frame, or mounted in any way, to be hung
ou a wall, as in the case of an ordinary clock.
The bimetallic thermometer may be made of other form than a ring, as for
example, of horse-shoe shape.
Referring to the accompanying sheet of drawings Fig. 1 is a front view of a
thermometer according to this invention, arranged in a frame suitable for attach-
ment to a wall. Fig. 2 is an elevation of the dial plate as seen from behind;
Fig. 3 is a section in line a. b, Fig. 2; Fig. 4 is a plan with the frame removed;
Fig. 5 is a section in line c-d, Fig. 1; Fig. 6 shews an instrument according to
this invention mounted on a stand; Fig. 7 is a back view of the same to a large
scale, with the stand removed; and Fig. 8 is a section in line e, f, Fig. 7.
Like letters of reference indicate similar parts in all the figures.
Two strips of metal g and h having different coefficients of expansion are
soldered together and formed into an incomplete ring (Fig. 2) or horse-shoe (Fig. 7).
To one limb there is attached a bracket k from which project two racks k¹, k¹. To
the other limb there is affixed by an elastic connexion a rack ', situated sym-
metrically with regard to the other two-Between the two sets of racks there
is carried an axis q formed of pinion wire, which has no other bearing. The
incomplete ring or horse-sboe g. h is held by the bracket i midway between its
two limbs which have equal and opposite motions, or approximately so, and these
motions are converted into a rotary motion of the axis by means of the two sets of
racks. The index m carried by the axis q moves over a graduated dial (Fig. 1),
and is enclosed in front by a plate of glass. n. n (Fig. 2) are two guards, and o
(Fig. 3) is a stop to prevent the axis moving endwise during transit; p is a back
plate.
Having now particularly described the nature of the said invention and the
manner of performing it, I desire to have it noted that no general claim is made to
the use of a compound metallic ring or horse-shoe as being new, nor do I claim the
mode of indicating the temperature by means of a dial and pointer, but I hereby
declare that what I do claim is
1. In a metallic thermometer with dial-supporting the axis of the index with-
out fixed bearings between moving racks or pieces which experience equal and
opposite movements (or approximately so) under changes of temperature substan-
tially as described.
2. Metallic thermometers with dials constructed arranged and operating sub-
stantially as described with reference respectively to Figs. 1 to 5 inclusive and to
Figs. 6 to 8 inclusive of the drawings annexed.