Improvements in Instruments for Measuring Distances on Maps, Plans, and the like.
Year: 1897

page_text: Date of Application, 7th Oct., 1897-Accepted, 20th Nov., 1897
COMPLETE SPECIFICATION.
Improvements in Instruments for Measuring Distances on Maps,
Plans, and the like.
I, JOHN HENRY JACK, of 19 and 20 Holborn Viaduct, London, Patent Agents
Clerk, do hereby declare the nature of this invention (communicated to me by
Joseph Camille Marie Bonnefoi of 6 Rue du Havre, Paris, France) and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:-
-
The curvimeter forming the subject matter of my invention apart from its
great simplicity and great strength, possesses the important advantage of permit-
ting of gauging, direct, the exact distances between places, on a map, without
the necessity off first referring the instrument to a scale as is the case with the
ordinary curvimeters. Thereby measuring distances is rendered a very rapid
and very easy operation, which is a particular advantage to officers on service in
the field.
My instrument comprises, essentially, a spurwheel with teeth to a number
representing a multiple of ten, and the extreme points of which are at such dis-
tance from each other as on the scale of the map for which the instrument is
designed will represent one hundred metres. At every tenth tooth, the wheel
is provided with a pin projecting laterally, and while the wheel is made to
travel on the map these pins, in succession, come into contact with the free end of
a flat spring which is thereby made to vibrate so as to emit a sound.
The annexed drawing shows a curvimeter arranged in this way.
Fig. 1. is a front view.
Fig. 2. is a side view.
Fig. 3. is a back view partly in section.
A. is the spurwheel which in the example shown is provided with twenty teeth,
and, hence, with two pins B. The spurwheel is mounted in the forked bracket C.
in which it runs with sufficient friction to admit of its being raised off the map
without fear of its turning. On the face opposite to that which bears the pins,
the spurwheel is numbered in kilometres and graduated from 500 metres in order
to facilitate computation.
D. is the flat spring which comes into contact with the pins B. so as to ring,
at every.kilometre. In the example shown this spring terminates in a little rod
which is wormed and which screws into the base of the fork C. However, I do
not limit myself to this mode of fixing of the flat spring nor even to the employ-
ment of any flat spring of this kind, the essential feature, in my system, being that
of having an audible signal at the end of each kilometre traversed, whatever the
arrangement adopted in order to obtain this result.
In order to use my curvimeter, the operator should run it along on the map,
so as to follow the line to be measured and taking care to see that, to commence
with, point No. 1. of the spurwheel is made to rest on the point of departure; it
will then suffice to count the number of sounds heard in order to
ascertain the number of kilometres intervening between the point of
.
077

page_text: departure and that of the destination, and to count the number of tooth-points
intervening beween the pin which has passed last over the map, and the tooth-
point which comes nearest to the point of destination on the map, in order to
ascertain the number of hectometres to be superadded to the number of kilo-
metres indicated by the sounds emitted.
I may add that my curvimeter may be used as an ordinary curvimeter on a
map drawn to a scale differing from that for which the instrument is designed,
that is to say that in this case, after having run the wheel on the map it is made
to run the same number of revolutions on the scale, in order to ascertain the
distance between the point of departure and the point of destination.
1
Having now particularly described and ascertained 'the nature of my said In-
vention, and in what manner the same. is to be performed, I declare that what I
claim is: :-
The improved measuring instrument having an audible indicator arranged and
operated, substantially as set forth and as shown by the accompanying drawings.
Dated this 7th do'r of Datahan 1907
J. E. EVANS-JACKSON. & Co.,
Agents for the Applicant.