Pfaff 260 Service Manual page 28

To ensure that the cam assembly will rotate only when the needle is out of the
material, the position of the driving eccentric (Figs. 79 and 80) on the arm
shaft must be adjusted in proper relation to the needle bar crank (105057). Dur-
ing each revolution of the arm shaft, the driving lever rna kes one sideways
motion and, through a connecting lever (50371 ), rotates the cam assembly by
a fraction of one revolution (intermittent feed) .
The com assembly naturally must revolve in one direction only and, in addi-
tion, must be retained in its position each time the driving lever returns for its
next stroke. This requirement has necessitated the incorporation of a feed
clutch assembly made up of a roller clutch (50473) and a clutch body (50483)
with a backlash
retain~r.
The exchangeable cam assembly is secured in posi-
tion on the collar of the clutch body by a beehive spring and a thumb nut
(a in Fig. 51).
Eight feeler fingers, arranged spirally around a center stud and offset at an
angle of 45° against one another, make up the feeler finger assembly (t in
Fig. 111 ). Cam selector dial D (Fig. 111) has eight graduations, one for each
feeler finger. By turning this dial one eighth of a turn at a time, each feeler
'
finger is set alternately to engage the cam opposite. All possible settings of
the feeler finger assembly can be covered with one complete turn of dial D.
As the cam assembly rotates, the feeler finger rides on the rim of the corre-
sponding pattern cam and transmits its rhythmic throws to the feeler finger
assembly carrier (50386), an adjustable connection (50400), ond the engaging
lever driver (50499).
This driver carries three studs (50498) each of which is provided with a slot to
receive one of the th ree engaging levers (50431, 50585, and 50599). Two of
these levers are hinged to a connecting rod (105193), and one to the zigzag
regulator arm (106178).
The front and central engaging levers control the stitch width and are secured
in the two holes of the connecting rod by means of eccentric studs. Since each
hole is arranged at a different distance from the fulcrum of the connecting
rod, the engaging lever connected to the lower of the two holes will cause the
zigzag regulator stud (106177) to make a larger rotation than will the engaging
lever secured in the top hole. In addition, the ·front stud makes a larger side-
ways motion than do the two others.
All motions are adapted to one another so that the front engaging lever con-
trols the needle motion for the entire width of bightJ while the central engaging
lever controls the needle motion only for half the needle throw.
The needle position is controlled by the rear engaging lever whose stroke is
the shortest of them all and actuates the zigzag regulator arm.
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