AN IMPROVED DRAWING INSTRUMENT
Year: 1865

page_text: PROVISIONAL SPECIFICATION left by George Clark at the Office of
the Commissioners of Patents, with his Petition, on the 14th July
1865. A communication from abroad by Mr. Garcia de Morales, of
No. 33, Rue de Liedekerke St. Josse-ten Noode, Brussels, Belgium.
I, GEORGE CLARK, of No. 2, Napier Street, Dover Road, in the County
of Surrey, do hereby declare the nature of the said Invention for "AN IMPROVED
DRAWING INSTRUMENT," to be as follows:
The object of this Invention is to enable draughtsmen and engravers to
produce parallel and equidistant lines on plans, elevations, and drawings on
paper, stone, or metal, with greater facility, expedition, and accuracy than by
any of the methods in use.
This object is effected by the construction of an instrument, of which Plans
and Drawings are hereunto annexed, and of which the following is a description,
with references to such Plans and Drawings:
Fig. 1 is an elevation, and Fig. 2 a profile of the instrument; Fig. 8 is a
plan shewing the application of the instrument; Fig. 4 is an elevation shewing
the action of the instrument. The same letters indicate the same parts of the
instrument in the several Drawings. (a) is a lever; (b, b,) are supports to
the. lever; (c) is the pivotting screw and fulcrum to the lever; (d) is a steel
spring fastened to the lever by the screw (e); (f) is a shifting foot; (g) is a
pin to the foot; (h) is a regulating screw; (i) is a screw fastening the sup-
ports to the square (j); (k) is a hole in the square; (2) is a flat rule; (m)
is work executed by the instrument.

page_text: The mode of using and the action of the instrument are as follows:-In
Fig. 8 (m) represents the work of the instrument, in parallel lines colored red,
and (2) is a flat rule guiding the action of the instrument, shewn in red out-
line. The latter is held down firm by one hand, so that the square (j) may
slide against it, and with the same hand the square (j) is held securely, so
that it cannot separate itself from the flat rule (1). Supposing the first line
of the work to be drawn, a finger of the hand in which the drawing pen is
held is pressed upon the regulating screw (h) on the lever (a), depressing the
lever (a) which is balanced on the pivot screw (c), which passes through the
supports (b, 6), the supports (b, b,) being fixed to the square (5) by the screw
(i). This movement of the lever (a) gives to the foot (f), of which the
extremity is tapered to a knife-edge, and passes through the hole (k) of the
square (j), a point of resistance on the paper or metal on which lines have to
be produced. From this action it follows that the foot (f) being fastened to
the lever (a) by the pin (9) on which it turns, communicates to the square
(j) a receding or backward motion, after which the finger being removed
from the regulating screw (h) the next lime is drawn, and so on; the lines are
drawn successively. The result is the work (m) shewn in Fig. 3; the spring
(d) fixed to the lever (a) by the screw (e) bears upon the foot (f.), so that
the moment the contact of the finger leaves the regulating screw (h) the
lever (a) and the foot (f) are restored to the position indicated in Fig. 1.
The spaces between the parallel lines produced by the instrument may be
indefinitely varied, according as the lower extremity of the screw (h) which
regulates the action of the foot (f) is brought nearer to or further from the
square (j).