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M E C H A N I C A L
P R I N C I P L E S
2 1
When the punch clutch is not engaged, the gen-
eva
awl
rides on the surface of the one-tooth
ratchet during the greater part of the cycle. When
the pawl reaches a point opposite the single tooth,
the tail of the pawl strikes the
awl
disengaging
roller (Figure 2 1 ) and is cammed away from the
ratchet until it has moved past the point where
it may engage in the single tooth of the ratcher.
By cranking the machine by hand, it can be noted
how the pawl disengaging roller prevents the ge-
neva pawl from engaging.
From the above, it is
evident that the operation of the geneva pawl is
controlled by the pawl disengaging roller.
The
pawl disengaging roller is mounted on a triangular
plate (Figure 2 1 ) which is free to pivot on the
latch cam roller arm. The latch cam roller arm
(Figure 2 2 ) is operated by the latch cam which
turns only when the punch clutch is engaged.
When the punch clutch is engaged, the latch cam
turns, causing the latch cam arm t o rotate in a
counterclockwise direction. As the latch cam arm
rotates, the upper end moves to the left and down
allowing the pawl disengaging roller to move past
the single revolution timing cam and the geneva
pawl to engage in the one-tooth ratchet.
As the
cycle is completed, the larch cam causes the latch
cam arm to rotate in a clockwise direction carrying
the pawl disengaging roller to the right. The rol-
ler strikes the tail of the geneva pawl and disen-
gages the pawl from the one-tooth ratchet when
the roller is backed by the single revolution timing
cam.
Single Revolution Timing C a m
The geneva disc has
7
cuts in it and moves the
card one cycle point for each cut. The machine is
a fourteen point cycle machine; therefore, the gen-
eva disc must make two revolutions per machine
cycle, which means that the geneva pawl will pass
the pawl disengaging roller twice during each
cycle. The purpose of the single revolution timing
cam is to prevent the feed rolls from stopping in
a position half way through a cycle. At the end
of the first revolution of the geneva pawl and disc,
the flat side of the single revolution timing cam
should be down (Figure 2 2 ) . The pawl disengag-
ing roller is free to swing away from the tail of
the pawl. Therefore, in case the geneva pawl had
become disengaged from the one-tooth ratchet, it
would be free to drop into the one-tooth ratchet
on the next revolution to complete the cycle. This
assures that the pawl will not be disengaged by the
pawl disengaging roller until the punch unit mech-
ansim has reached its proper latching position and
that the geneva makes two revolutions for each
cycle.
Principle o f Punching
The mechanism for punching holes consists of
80 individual punches, each controlled by an in-
/
Cam Assembly
terposer, 80 punch magnets together with arma-
Geneva Pawl
Disengaging Roller
(Pinned to this
shaft which carries
tures and pull wires to control the 80 interposers,
punch clutch pawl)
.
a punch bail to drive the punches through the card,
and the eccentric drive shaft and links to operate
L\-<j
the punch bail. There is a separate punch for each
card column; any one punch may be required to
punch any hole from
9
to 12. The cards feed in
,
I
' ,
' /
.___.',
9 edge first, and every 9 to be punched is punched
:
0
at the same time. The card then moves t o the 8
Figure 22. Single Revolution Timing C a m
position and every 8 is punched, and so on until
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