AN IMPROVED INSTRUMENT OR APPARATUS FOR THE LINEAR MEASUREMENT OF DRAWINGS OR PLANS
Year: 1879

page_text: PROVISIONAL SPECIFICATION left by William Robert Lake at the Office of
the Commissioners of Patents on the 10th April 1879. A communication
from abroad by Joseph André Fresco, of Angers, France, Mechanical Dentist.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. "AN IMPROVED INSTRUMENT OR APPARATUS FOR
THE LINEAR MEASUREMENT OF DRAWINGS OR PLANS." [A communication from
abroad by Joseph André Fresco, of Angers, France, Mechanical Dentist.]
My Invention relates to an improved instrument which is designed to indicate
immediately and by a single operation on a dial or dials the measurement or length
of a line or lines upon a drawing or other design, however many curves or sinuosities
there may be in such line or lines.
I am aware that an instrument has been heretofore constructed for a similar
purpose and which partially effected the above named object, but with the exception
of the toothed wheel or roller which is caused to run upon the paper, and which is
the only part common to the two instruments, my improved instrument differs
entirely from that heretofore constructed. In the latter the wheel or roller in
turning moves lengthwise upon a screw which extends its axis of rotation, and it is
necessary in order to obtain the desired measurement to turn the wheel or roller in
a contrary direction upon a graduated scale. By my improved instrument I
dispense with the latter operation by means of a wheel or roller in connection with
a very simple system of gearing, and with hands moving upon dials and denoting
instantaneously in kilometres or fractions of a kilometre or other divisions the
measurement of the line traversed.
In constructing an instrument according to my Invention to indicate French
measurements I provide the same with two dials, one of which indicates the
measurement of any distance up to twenty kilometres, and the other dial multiplies
them by twenty kilometres in such a manner that by the combination of these
dials I can obtain an indication up to 200 kilometres.
On the side of the said instrument opposite to the dials is placed a compass to
facilitate the placing of the cardinal points upon a drawing or plan.
The rod or handle of the said instrument is provided at its extremity farthest
from the aforesaid dials with a crayon or pencil holder, and its four sides are
provided with different scales. Over the aforesaid dials two hands are arranged to
move, and are caused to rotate by the aforesaid toothed wheel or roller which

page_text: projects beyond the bottom of the apparatus, and which is caused to revolve in
travelling over the paper or other material between the points whose distance apart
it is desired to measure.
In the interior of the said instrument or apparatus are provided two gear wheels,
one of which is put in operation by a pinion fixed on the axis of the aforesaid
wheel or roller, the other gear wheel being rotated by a pinion on the axis of the
first named gear wheel.
On the axes of the said gear wheels are fixed the hands of the two dials. A
spring pawl arranged in connection with the aforesaid small toothed wheel or roller
to prevent any backward movement of the same, and the said pawl also ensures
the regular and proper movement of the hands.
In using my improved instrument it is necessary first of all to bring the hand of
the first named or large dial to its proper starting point, and then to note the
number indicated by the hand on the other or smaller dial. The driving wheel or
roller is then rolled between the two points whose distance apart it is desired to
measure. The large dial then indicates the number of kilometres up to twenty, and
the smaller dial indicates the number of times twenty kilometres has been reached
in the distance traversed.
In some instances I employ a stud or button to return the dial hands to their
starting point after manipulation of the instrument; and I may also in some cases
sink one of the dials below the surface of the other, in which case the two hands
will turn upon the same centre, the one marking the units and the other multi-
plying them.
It is evident that the scales upon the rod or handle of the instrument may be
adapted to the scales of measurement adopted in different countries.