An Improvement in Metallic Thermometers and Barometers.
Year: 1894

page_text: Date of Application, 12th Apr., 1894
Complete Specification Left, 2nd Aug., 1894-Accepted, 8th Sept., 1894
PROVISIONAL SPECIFICATION..
An Improvement in Metallic Thermometers and Barometers.
"
I, THOMAS WHEELER, of 8 Coombs Street, Haverstock Street, City Road,
London, Aneroid Barometer Maker, do hereby declare the nature of this invention
to be as follows:-
My invention relates to an improvement in metallic thermometers of that kind
in which the variations of temperature are measured by the variations of curvature
of a compound metallic segment or of a Bourdon tube filled with a highly
expansible liquid.
These instruments are combined in one case with an aneroid barometer, the
indications of the two instruments being recorded on separate dials arranged like.
the minutes and seconds dials of a watch, but the improvement is equally applicable
whether the thermometer be combined with a barometer or not.
The object of the improvement is to simplify the construction of the instrument,
to render more direct the transmission of the motion from the part of the instrument
which is influenced by heat to the arbor of the index by which the extent of such
motion is denoted, and. to diminish the error which is incidental to the use of the
toothed rack and pinion generally employed for transmitting such motion.
The improvement consists in transmitting the motion in the one direction through
a chain coiled about a pulley on the index arbor, the chain being attached to the
outer or movable end of the compound curved bar or segment, or of the Bourdon
tube, as the case may be, directly or through a radially projecting arm by which
the requisite leverage is obtained to multiply the extent of motion, the move-
ment in the other direction being produced by a hair spring coiled about the
index arbor whereby a substantially constant tension is applied to the chain and
compound segment or tube whose variations of curvature are thus closely followed
by the index.
The invention is applicable also to metallic barometers.
1
11001
$
COMPLETE SPECIFICATION.
An Improvement in Metallic Thermometers and Barometers.
1, THOMAS WHEELER, of 8, Coombs Street, Haverstock Street, City Road,
London, Aneroid Barometer Maker, do hereby declare the nature of this invention,
and in what manner the same is to be performed, to be as follows:-
My invention relates to an improvement in metallic thermometers and barometers.
By a metallic thermometer is meant an instrument of that kind in which the
variations of temperature are measured not by mercury but by the variations of
curvature of a compound metallic segment or of a Bourdon tube filled with a
highly expansible liquid.
A metallic thermometer is usually combined in one case with an aneroid
barometer, the indications of the two instruments being recorded on separate dials
[Price 8d 1

page_text: In the accompanying drawings, forming part of this Specification,
Figure 1 represents a face view of one arrangement of the mechanism of the
thermometer. Figure 2 represents a transverse section of the same, upon line 2-2
Figure 1, and Figure 3 represents a similar section, on line 3-3 Figure 1; all
these figures being drawn about four times full size.
Figure 4 is a face view of the dial, full size, for which the arrangement of
mechanism shewn in the other figures is designed.
The same letters of reference denote like parts in all the figures.
A is the part of the instrument influenced by heat, said part being, in this
example, a spirally coiled Bourdon tube whose inner end is fixed to the extremity
of an arm B secured by a screw b to the back of the dial plate C of the instrument.
To the outer end of the tube A is affixed an outwardly projecting radial arm a to
whose extremity is attached one end of a chain D of which the other end is
connected to, and coiled upon, a pulley E fixed on the arbor f of the index F.
The index arbor fis mounted in a cock G fixed upon the plate C, as usual, and to
said arbor is attached the inner end of a hair spring H whose outer end is fastened
to a stud h, the spring being coiled in the opposite direction to the winding of the
chain D upon the pulley E so that it will act in opposition to the expansion with
heat of the spiral tube A.
The mechanism of the aneroid barometer is not illustrated, as it is the same as
usual.
In the example illustrated, the thermometer index F works over a small dial
eccentric to the dial of the aneroid, but it will be evident that if the thermometer
be used alone the arborf of the thermometer index will be located at the centre of
the dial plate C. The construction is similar when a compound metallic segment
is used instead of a Bourdon tube.
Figure 5 shews a modified arrangement in which both the centre about which
the Bourdon tube A is coiled and the arbor f of the index F are concentric with
the dial plate C, the advantage of this arrangement being that it enables a larger
tube or a smaller dial to be used. In this case the chain D passes from the end of
the Bourdon tube round a pulley d and thence to the pulley E on the index axis f
80 as to apply the pull due to the expansion of the tube, in the most effective
direction for rotating the index F.

page_text: Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, 1 declare that what I
claim is :-
In a metallic thermometer or barometer, the herein described means for trans-
mitting motion to the index arbor, consisting of a chain or its equivalent attached
directly or through a radially-projecting arm to the outer end of the Bourdon tube
(or compound bar) and to à pulley on the index arbor, in combination with a volute
hair spring applied to act on the index arbor, substantially as specified.
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.