Improvements in Aneroid Barometers for Facilitating the Reading of Pressure Changes.
Year: 1889

page_text: Date of Application, 12th Feb., 1889
Complete Specification Left, 12th Nov., 1839-Accepted, 12th Feb., 1890
TRUYIDIONAL DIRECTIVATION.
Improvements in Aneroid Barometers for Facilitating the Reading
of Pressure Changes.
1, JOHN THOMAS DANIELS of 14 Smith Street, Northampton Square, London, E.C.,
do hereby declare the nature of this invention to be as follows:-
This invention relates to improvements in aneroid barometers whereby the variations
of atmospheric pressure may be rendered more readily apparent and indicated with
greater accuracy than can be done by the ordinary single needle barometer the move-
monts of which usually extend over only a fractional portion of the dial.
My invention consists in employing two needles cach travelling around a separate
dial one dial being graduated to indicate the inches or other units of pressure and
the other graduated to indicate the fractions or subdivisions thereof. To effect this I
fix a toothed pinion to the upper end of the axis which usually carries the pointer,
at the same time connecting the chain and hair spring to this spindle in the usual
manner.
Gearing with the pinion aforesaid are two smaller pinions one of which carries on
its axis the pointer for indicating the inches or other units of pressure whilst to the
axis of the other is fixed the pointer for indicating the subdivisions of the said units.
Tho dials may be adjusted to zero by any suitable means.
To diminish friction the edges of the larger pinion may be bevilled so as to reduce
the amount of surface contact between the teeth of this pinion and those of the
other two. The relative size of the pinions is arbitrary and may be varied according
to circumstances.
Dated thin 10th 1140n
COMPLETE SPECIFICATION.
Improvements in Aneroid Barometers for Facilitating the Reading
of Pressure Changes.
I, JOHN THOMAS DANIELS of 14 Smith Street, Northampton Square, London E.C.,
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:-
This invention relates to improvements in aneroid barometers whereby the variations
of atmospheric pressure may be rendered more readily apparent and indicated with
greater accuracy than can be done by the ordinary single needle barometers the move-
ments of which usually extend over only a fractional portion of the dial.
My invention consists in employing two needles each travelling around a separate
dial one dial being graduated to indicate the inches or other units of pressure
and the other graduated to indicate the fractions or subdivisions thereof. To effect
this I fix a toothed pinion to the upper end of the axis which usually carries the
pointer at the same time connecting the chain and hair spring to this spindle in
the usual manner.
Gearing with the pinion aforesaid are two smaller pinions one of which carries on its
axis the pointer for indicating the inches or other units of pressure whilst to the axis
of the other is fixed the pointer for indicating the subdivisions of the said units.
The dials may be adjusted to zero by any suitable means. To diminish friction the
edges of the larger pinion may be bevilled so as to reduce the amount of surface
contact between the teeth of this pinion and those of the other two. The relative size
of the pinions is arbitrary and may be varied according to circumstances.

page_text: In the accompanying drawings Fig. 1 represents a plan of an aneroid barometer
constructed according to my invention Fig. 2 is a section thereof taken through the
dotted line, and Fig. 3 is a view of the complete instrument.
As the general construction of the barometer is identical with those heretofore made
I shall only refer to such parts as are essentially connected with my invention.
These consist of a base plate A. secured to the back plate of the instrument at a
suitable height therefrom such base plate forming a bearing in which are pivotted
the inner ends of the arbors of two pinions b and c the other ends of these arbors
being pivotted in a bracket B screwed permanently to the plate A.
A third pinion a is mounted in a cock surewed adjustably to the plate A as
hereinafter described. To the arbor of the pinion a are attached the ordinary hair
spring e and chain and on the arbors of the pinions & and c are mounted pointers g
and revolving about dials and k. The pinion a gears with the both of the
pinions b and c and the surface motion of the pinion a is communicated to the said
pinions oqually but it is obvious, that the circular motion of the pinions will
vary in proportion to their relative diameters and that an imperceptible motion of
the pinion a whilst producing a scarcely perceptible motion of the pinion might
produce a distinctly perceptible motion of the pinion c which motion would be
rendered much more distinct on account of the length of its pointer. The function
of the pointer g may therefore be compared to that of the "minute" hand of a
watch and that of the pointer to the "seconds" hand. Owing to the extreme
delicacy of the teeth of the pinions it will be readily understood that in order to
ensure perfect working means must bo provided whereby the pinion a can be caused
to goar with the greatest nicety with the pinions band c. Those means in the
present instance consist of three lateral screws by the use of which the cock C can
be adjusted to any desired position.
It must be understood that although 1 have described the use of three pinions and
two pointers 1 do not confine myself either to the number or the disposition of the
parts as shown in the drawings as various modifications may be employed without
departing from the essential features of my invention namely the employment of
multiplying pinions in aneroid barometers.
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 an aneroid barometer the combination of pinions a band cand pointers g and h
substantially as and for the purpose herein sot forth and illustrated in the accompany-
ing drawings.
2. In an aneroid barometer the combination of a pinion such as a actuated by chain
and hair spring with a second pinion of smaller size operating a pointer.
8. In an aneroid barometer the combination of a pinion such as a actuated by chain
and spring and actuating a pointer mounted axially, with a pinion of smaller size also
actuating a pointer mounted axially for the purpose herein described.
4. In a barometer such as described the use of adjusting screws for determining the
position of the bracket C and wheel a with regard to the wheels band o substantially
as and for the purpose described and illustrated in the accompanying drawings.
JOHN THOMAS DANIELS.