For this purpose all kinds of velvet may be employed, and, in order to
facilitate the cutting, they are previously coated on the reverse side
with any glue or gum whatever, which gives the velvet a stiffness
favorable to the action of the punch. To effect the object desired the
apparatus has three successive operations to perform: first, cutting the
circles; second, moistening; and third, fastening down the dots upon the
tissue according to a definite order and spacing. The machine may be
constructed upon any scale whatever, although at present it is only made
for operating on pieces 31 inches wide, that being the normal width of
dotted tulles. The quincuncial arrangement of the dots is effected by
the punching, moistening, and fastening down of odd and even dots,
combined with the forward movement of the tissue to be chenilled.
The principal part of the machine is the cam-shaft, A (Figs. 1, 2, and
3), which revolves in the direction of the arrows and passes in the
center of 80 cam-wheels, 40 of which are odd and 40 even, alternately
opposed to each other. This shaft actuates, through its two extremities,
the different combined motions in view of the final object to be
attained, and also carries the motive pulleys, PP'. Figs. 1 and 2 show
the profile of two of these opposed cam-wheels--the arrangement by means
of which two rows of dots (odd and even) are laid down upon the tissue
during one revolution of the shaft or drum, A. Each of the wheels
carries three cams (Figs. 1 and 3), the first, (_a_), corresponding to
the punching; the second, (_a'_), to the moistening, and the third,
(_a''_), to the gluing down of the dots.
The annexed figure, one-quarter actual size, shows in section the
details of the cutting mechanism. To each cam-wheel there corresponds
one punch, and the eighty punches are arranged side by side and parallel
upon a shaft, B, a spring, _b_, holding them constantly against the
circumference of the cam-wheels. In Fig. 2 only one of these details is
shown. The punching arrangement consists of an ordinary punch, _c_, of
variable diameter, screwed to the extremity of a tube, _d_, which is
itself suspended from the end of the lever, _p_, but which can receive
from it at the desired moment the pressure necessary to effect the
cutting. The vertical position of these multiple tubes is insured by
a guide, _e_, which is thoroughly indispensable. Through each of the
tubes, _d_, there passes a plunger designed for expelling from the punch
the piece that has been cut out of the velvet, and for gluing it down to
the fabric. The two small springs, _b'_ and _b''_, tend continually to
lift the tubes as well as the plunger. The whole mechanism is affixed to
solid cast-iron frames, and the machine itself may be mounted on wooden
supports or a metal frame.
The punching is effected on a bronze straight-edge, C, which slides in a
cast-iron channel, D. This presents alternately, in its movement, entire
and punctured spaces, the former for receiving the blow of the punch and
the latter for allowing passage at the desired moment to the plunger
as it goes to fasten the dots upon the tulle which is passing along
underneath the channel, D. The punching is done primarily and
principally by pressure, but, in order to facilitate the complete
detachment of filaments which might retain the punched-out piece, the
punch is likewise given at the same time a slight rotary motion, thus
imitating mechanically what is performed by hand in the maneuver of all
punches. This rotary motion is communicated to the punches by means of
levers actuated by an eccentric, E, and which move the frame, _h_, whose
bars engage with the horizontal lever, _g_, soldered to the tube, _d_,
thus causing the latter at the very moment the punch descends to revolve