Machines
incorporating
the principle
of
direct
needle
bar
frame control
work
differently. They
ore
so
designed
that
both the
zigzag
regulator
stud
and
the
needle
bar
frame
ore
operated
from the
pattern
com
direct
(see Fig. 44); in
other
words, the
sideways
motion
of
the
needle
bar
frame
is
not derived from
on
eccentric.
Each
pattern
com normally produces only
one
basic
embroidery
design.
To
change
over from
one
design
to
another,
a
new
pattern
com must
be
inserted
in the machine.
Mecftanical
Principle
of
the
Pfaff
-261
Automatic
Both the Pfaff 260 flat-bed
and
the Pfaff 360 free-arm sewing machines
are
so
designed
that
they
con
be
converted into
automatic
machines
at
any
time.
The
automatic
embroidery
mechanism used
for
these
machines
con
be
easily
installed in the mochin·e arm. This arm, which
is
open
at
the
top,
is
closed with
a
special
top cover supplied with the
automatic
embroidery
mechanism.
In
contrast
to
automatic
devices which
ore
so
designed
that
the throw
of
the
pattern
com
is
transmitted
to
the needle
bar
frame
· directly (Fig.
44),
the
Pfaff
automatic
embroidery
mechanism controls the
need
le motion indirectly,
i.e
.
through the
needle
position
and
stitch width
regulator
assemblies.
As
a result,
1
Fig.
44
Diagram showing the mechanical principle
of
direct needle
bar
frome control
7
1 = Pivot
2 = Feeler finger
3
= Pattern cam
4
= Slide block
5 = SloHed lever
6 = Pivot
7 =
Needle
bar
frame pitman
8
=
Needle
bight
9 =
Needle
plate
10
=
Needle
bor
11
=
Needle
bar
frame
0 =
No
needle throw (straight stitch)
23