Improvements in Maximum Thermometers.
Year: 1892

page_text: Date of Application, 15th Nov., 1892
Complete Specification Left, 14th Sept., 1893-Accepted, 28th Oct., 1893
PROVISIONAL SPECIFICATION.
Improvements in Maximum Thermometers.
ALFRED ERNEST DEAN Meteorological Instrument Maker 230 South Lambeth
Road Claphain London do hereby declare the nature of this invention to be as
follows:-
In a Specification dated July 12th '92 No. 12743 I have shewn an improved
method of constructing clinical thermometers. I have since discovered that the
same principle of construction can, with certain modifications, which I am about
to describe, be applied to the construction of an ordinary maximum thermometer.
I construct such a thermometer in the following manner : Above the bulb
containing the mercury I produce a constriction in the thermometer stem in the
ordinary way; by so doing I reduce the bore of the thermometer tube to such an
extent that the mercury which passes it in flowing out of the bulb, will not pass
back again, if the thermometer be laid in a nearly horizontal position, but I do
not reduce the said bore so much as to prevent the reflux of the mercury into the
bulb if the thermometer be raised into a perpendicular position & there be a
considerable length of mercury column in the thermometer tube.
These so far are features common to my improved thermometer & the well
known maximum thermometer of the Negretti type. My improvement consists in
providing means by which a thermometer of this type may be automatically set,
that is without shaking, tapping, or any violent movement & by a mere change
from a nearly horizontal to a nearly perpendicular position.
This I do by providing at the end of the tube opposite to the bulb already
mentioned a smaller bulb or cavity of suitable shape & of sufficient capacity to
hold an amount of mercury proportioned to the quantity of mercury which the
bore of the thermometer can hold.
I furthermore reverse the scale upon this thermometer; so that for reading it
the mercury is caused to flow into & fill this cavity & the reading is obtained by
observing the length of the mercury column which cannot be so accommodated.
I am able in this way to secure that, even with the lowest reading on the
thermometer, there shall be in the thermometer tube, when placed in an erect
position, a sufficient length of mercury column supplied from the mercury which
flows out of the cavity to force the passage of the constricted part of the
thermometer tube and fill the principal bulb.
By this improved construction I form a thermometer which automatically sets
itself when placed as above described in an erect position.
November 15th 1892!
ALFRED ERNEST DEAN,
COMPLETE SPECIFICATION.
Improvements in Maximum Thermometers.
I, ALFRED ERNEST DEAN, Meteorological Instrument Maker, of 230 South
Lambeth Road, Clapham, 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 :-
In the Specification of Letters Patent granted to me dated July 12, 1892,
No. 12743, I have shown and described an improved method of constructing
clinical thermometers.
1

page_text: .
I have since discovered that the same principle of construction can, with certain
modifications which I am about to describe, be applied to the construction of an
ordinary maximum thermometer.
I construct such a thermometer in the following manner.
Above the bulb containing the main body of mercury, I produce a constriction
in the thermometer stem in the ordinary way; by so doing I reduce the bore of
the thermometer tube at such part to such an extent that the mercury which
passes it in flowing out of the main bulb will not pass back again if the thermometer
be held in a horizontal or nearly horizontal position, but I do not reduce the said
bore so much as to prevent the reflux of the mercury into the said bulb if the
thermometer be raised into a more or less nearly perpendicular position and there
be a considerable length of mercury column in the thermometer tube.
The above features are common to my improved maximum thermometer and the
well known maximum thermometer of the Negretti type.
My present improvement consists in providing means by which a thermometer of
this type may be automatically set, that is to say, without shaking, tapping, or
any violent movement, and by a mere change from a more or less nearly horizontal
position to a more or less nearly perpendicular position.
This I do by providing at the end of the tube opposite to the main bulb
already mentioned, a smaller bulb or cavity of suitable shape and of sufficient
capacity to hold an amount of mercury proportioned to the quantity of mercury
which the bore of the thermometer can hold.
My invention is represented in the accompanying drawings, in which :-
Figures 1, 2 and 3 represent three positions of my improved maximum
thermometer, in which the scale is reversed in position as compared with an
ordinary thermometer, and Figures 4 and 5 represent a like thermometer in which
the scale is arranged in the ordinary manner.
In all the figures a represents the main bulb, the thermometer tube, 6' the
constriction in the tube and c the smaller bulb or cavity.
In using the maximum thermometer with reversed scale shown at Figures 1, 2, 3,
the thermometer is normally hung in the position shown at Figure 1; then, when
it is desired to take a reading, the thermometer is placed in the position shown at
Figure 2, or approximately so, in which position the mercury in the tube b which
has become severed from that in the main bulb a by the constriction 6', is caused
to flow towards and join that in the smaller bulb or cavity c, which latter becomes
filled, and the reading is obtained by observing the length of the mercury column
which cannot flow into the said smaller bulb or cavity c.
This small bulb or cavity c consists of two or more enlargements or cavities in
the tube b communicating with each other by a small neck or passage as shown;
this form of smaller bulb or cavity always retains its supply of mercury when the
thermometer is in a horizontal position and only releases it when the thermometer
is in an inclined or vertical position and receives a slight tap or shake.
The thermometer shown at Figures 4 and 5 is formed similarly to that shown at
Figures 1, 2, 3, except that the scale is arranged in the ordinary manner and an
air speck dis introduced into the tube b, as shown at Figure 5, to keep the
mercury coming from the bulb a separate from that coming from the smaller bulb
or cavity c.
When using the maximum thermometer with ordinary scale shown at Figures 4
and 5, the thermometer is normally hung in the position shown at Figure 4 and
the reading is taken when it is in such position, whilst when turned into the
position shown at Figure 5 the mercury flows from the smaller bulb or cavity c
down the tube b and forces that from the bulb a past the constriction b¹.
By the construction of maximum thermometer herein described I am able to
secure that, even with the lowest reading on the thermometer, there shall be in the
thermometer tube b, when placed in an erect position as shown at Figures 3 and 5,
a sufficient length of mercury column supplied from the mercury which flows out

page_text: of the smaller bulb or cavity c to force the passage of the constricted part 6¹ of
the tube b and fill the main bulb a.
By this improved construction I form a maximum thermometer which
automatically sets itself when placed, as above described, in an erect or nearly
erect position.
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. In a maximum thermometer, the combination of a main bulb a, a tube b, a con-
striction in such tube, a supply of mercury in the bulb a, a smaller bulb or
cavity at the end of tube b opposite to that of the bulb a, a supply of mercury in
connection with said bulb or cavity c, and a reversed scale, substantially as herein
shown and described and for the purpose stated.
2. In a maximum thermometer, the combination with a thermometer tube b, of
a constriction b¹, a main bulb a at one end of such tube, a smaller bulb or
cavity c at the other end thereof, a supply of mercury to each of such bulbs, and
an air speck between the two columns of mercury, substantially as herein shown
and described and for the purpose stated.
Dated this 14th dor of Sentember 1893
ALFRED ERNEST DEAN,
By Harris & Mills,
23, Southampton Buildings, London, W.C., Agents.