Improvements in Clinical Thermometers.
Year: 1892

page_text: Date of Application, 12th July; 1892
Complete Specification Left, 12th Apr., 1893-Accepted, 1st Julv. 1893
PROVISIONAL SPECIFICATION..
Improvements in Clinical Thermometers.
I, ALFRED ERNEST DEAN Meteorological Instrument Maker 230 South
Lambeth Road London do hereby declare the nature of this invention to be as
follows:-
In clinical thermometers made with an indestructible index a great difficulty is
experienced in redescending the mercury into the bulb or reservoir after action.
The object of my invention is to aid the operation of redescending the mercury
into the bulb, by increasing the weight of mercury in the capillary.
To attain this I construct my thermometer with a cavity at the end opposite the
bulb & I fill the bore or capillary of the tube & also a portion of the cavity, so
that the column is allways full of mercury, on the reading being taken, the
thermometer is reversed & the mercury falls into the cavity, & the overflow is the
reading surface of the thermometer viz. the mercury last separated from the mass
in the reservoir by the constriction, is the reading surface.
In this manner I have a greater weight of mercury separated from the mass in
the bulb.
This increased weight & length is redescended into the bulb with greater facility
than in the clinical as at present constructed.
This reversed operation also avails me of the space left between the 95 point &
the constriction in the ordinary clinical thermometer. In this space I place my
110 point & in this manner increase the length of range.
Hence a greater sensibility & readiness of action.
1041
1000
ALFRED E. DEAN.
COMPLETE SPECIFICATION.
Improvements in Clinical Thermometers.
I, ALFRED ERNEST DEAN, Meteorological Instrument Maker, of 230 South
Lambeth Road, London, 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, reference being had to the
accompanying drawing and to the letters marked thereon:-
In clinical thermometers made with an "indestructible" index a great difficulty
is experienced in causing the mercury to redescend into the bulb or reservoir after
action.
The object of my invention is to facilitate this operation. This object I attain
by increasing the weight of mercury.in the capillary.
The accompanying drawing represents a clinical thermometer constructed
according to my invention and having the scale arranged in a reverse position as
compared with the scales of clinical thermometers.
For the purpose of my invention, as shown in the drawing, I construct a clinical
thermometer with a cavity or chamber c at the end of the stem distant from and
opposite the bulb a, and charge the said thermometer with mercury or other
thermometrical fluid, which I will hereafter, for the sake of brevity, refer to as
mercury. I fill not only the bulb a, but also the capillary b, and I partly fill the
cavity or chamber c so that the capillary may be either full or partially full of
mercury while the temperature is being taken. It is of course impossible to take
a reading of the thermometer represented in the drawing while the capillary is full
[Price 8d 1

page_text: of mercury or while the column of mercury in the capillary is disconnected from
that in the cavity or chamber c. For this purpose therefore the thermometer
is reversed and the mercury thereby caused to fall to the farther end of the stem b
and fill the before mentioned cavity or chamber c, the remainder or overflow
standing in the capillary b and giving the temperature reading. It may happen
that the separated column of mercury in the capillary is not of sufficient weight to
fall away from the constriction under the force of gravity only. In that case it
must of course be shaken on to the reserve of mercury in the chamber c. The
reading surface is thus given by the mercury last separated by the constriction d
from the mass in the bulb a of the thermometer combined with that in the
chamber C, and in this arrangement it is necessary therefore to reverse the scale
upon the thermometer, so that the highest reading may be nearest the bulb a and
the lowest reading nearest to the said cavity or chamber c.
The advantage of this arrangement becomes manifest when it is desired to shake
back the mercury into the bulb a. In clinical thermometers of the ordinary
construction this is a matter of considerable difficulty, especially when the
constriction is very small, a feature that is otherwise advantageous since it minimises
the danger of accidental falsification of the reading. The difficulty of shaking
back the mercury increases as the mercury column shortens, a fact which is well
understood and susceptible of a simple and obvious explanation. The difficulty is
consequently greatest with low readings in a clinical thermometer as ordinarily
constructed and becomes greater and greater as the operation of shaking back
proceeds because the mercury column is thereby diminished. But in a clinical
thermometer constructed according to my invention the capillary 6 is, during the
operation of shaking back, supplied with mercury from the aforesaid cavity or
chamber c. This additional length and consequent additional weight of the
mercury column causes it to descend with greater facility than heretofore and is the
advantage which my invention is designed to secure.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. A clinical thermometer having, in addition to the ordinary bulb, a chamber or
cavity at the upper end of the stem, which chamber or cavity is partially or
entirely filled with mercury, substantially as herein shown and described, and for
the purpose stated.
2. In a clinical thermometer, the use of the chamber c serving to hold a reserve
of mercury which may be employed to facilitate the shaking back of the mercury
into the bulb a, substantially as herein described and shown in the accompanying
drawing.
3. In a clinical thermometer, the use of the chamber c in combination with a
reversed scale, substantially as herein described and shown in the accompanying
drawing.
1000+
ALFRED E. DEAN,
By Harris & Mille,
23, Southampton Buildings, London, W.C., Agents.