The accompanying engraving shows new form of stencil pen invented by
Mr. J. W. Brickenridge, of La Fayette, Ind. In Fig. 1 the entire
apparatus is shown in perspective; Fig. 2 is a longitudinal section of
the pen; and Fig. 3 is a vertical section of a portion of the driving
apparatus. In this instrument compressed air is used as a motive force
for driving the perforating needle. The inverted cup, shown in detail
in Fig. 3, has its mouth closed with a flexible diaphragm, which is
vibrated rapidly by a pitman having a convex end attached by its
center to the middle of the diaphragm. The pitman is reciprocated by a
simple treadle motion, which will be readily understood by reference
to Fig. 1.
[Illustration: BRICKENRIDGE'S PNEUMATIC STENCIL PEN.]
The cup has a small aperture covered by a valve to admit of the
entrance of air when the diaphragm is drawn down. The pen, shown in
detail in Fig. 2, has a cup and flexible diaphragm similar to the one
already described. The diaphragm rests upon the enlarged end of a bar
which carries at its lower end a perforating needle. The pen is
connected with the driving mechanism by a flexible tube. The needle
bar is pressed lightly against the diaphragm by a spiral spring.
When the treadle motion is operated the impelling diaphragm is
rapidly vibrated, and through the medium of the air contained in the
flexible tube it communicates motion to the pen diaphragm and
consequently to the needle bar and needle. If, while the needle is
reciprocated in this way, the pen is moved over the surface of the
paper, a line of fine perforations will be made. With this instrument
stencils may be made for making multiplied copies of maps, drawings,
and manuscripts.
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