the mechanical principle
of
positively controlling the
needle
motion
by
an
eccentric
has
been
preserved
in
this machine (Fig.
42).
Automatic machines
incorporating th
is
feature
offer
the
additional
advantage
that
the
needle
posi-
tion
and
the
stitch width can
be
varied
either
singly
or
jointly
and
that
all
patterns
can
be
sewn in different lengths without
altering
the
stitch density.
The
Pfaff
-261
automatic
embroidery
mechanism
features
a built-in, exchange-
able
cam
assembly
made
up
of
eight
pattern
cams
of
different
shape
(Fig. 97).
With the
aid
of
the
embroidery
design
dial, controls
A,
B, C,
D,
E
and
F
of
both
the
machine
and
the
automatic
embroidery
mechanism (
Fig
.
113)
can
be
set
to
produce
several hundred
attractive
embroidery stitches.
Another
advantage
afforded
by
this
automatic
embroidery mechanism is
that
the
rotational
speed
of
its cam
assembly
can
be
varied
at
will
by
setting the
pattern
length lever
(4
in Fig.
46)
anywhere
between 0
and
7.
All
basic
designs
can,
thus,
be
lengthened
or
shortened
while
reta
ining the stitch density.
A
ll
motions utilized in the
automatic
embroidery mechanism
emanate
from
an
eccentric which
is
arranged
on
the
arm
shaft
and
simultaneously serves
as
a set
collar
(6
in
Fig
. 46). Pressed
against
this eccentric
by
spring action
is
roller 1 which is carried
on
driving lever 2. As the
arm
shaft
rotates,
the
eccentric pushes the roller
and
the
driving lever sideways a
certain
distance.
The
amount
of
sideways motion determines the
rotational
speed
of
com
assembly
5.
In
order
to
provide a possibility
of
varying this speed, the eccentric
tapers
off
toward
the right
and
the position
of
the driving lever
can
be
varied
in relation
to
regulating slide 3.
As
a result,
the
number
of
stitches
per
cam
revolution
can
be
increased
or
decreased,
as
required (Figs. 45-47).
When
the regulating slide is
moved
to
the
right
as
far
as
it will
go,
the driving
lever roller
is
opposite
the
concentric
collar
of
the
eccentric
and
out
of
con-
tact
with
the
eccentric
so
that
the Iotter idles.
As
a result, the driving lever re-
mains
in i
ts
starting position (Fig. 45)
and
the com assembly
is
not
rotated.
The
automatic
embroidery
mechanism
is
completely
disengaged.
Key
to
drawings on opposite
page
1 - Roller
2
-
Driving lever
3
Regu
la
ting slide
4
-
Pattern length lever
5
-
Cam
assembly
6
-
Driving eccentric
for
automatic
embroidery mechanism
7 =
Arm
shaft
24
Continued
on
pa~e
26
VO
Pattern
cam
does
not
rotate
Vl - Maximum
amount
of
pattern
cam
rotation
V3
Medium
amount
of
pattern
cam
rotation
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