Lewis 17 - Page 26

24
AUTOMATIC TENSION RELEASE
See Plate 7 Page 40
87. A special mechanism used on Lewis Model 24-12 Machine.
88. The purpose of
the automatic intermittent
tension release is to pre-
vent dimples or indentations
from showing on the outside
or face side .of the mat~rial
when felling or b.lind stitch-
ing two pieces of cloth to-
gether. This mechanism
is especially desirable
when felling thin light-
weight goods.
89. ,:;r'o avoid indenta.:'
tions or dimples the stitch
that is taken in the canvas.
FigureR
portion is made with a normal tension and the stitch that is taken in the
facing.is made with a very loose tension in order to allow sufficient
.thread between the two layers of material. In other words, the facing
and the canvas are not drawn tightly together through the operation of
the automatic tension release.
90. The purpose in setting the stitch in the canvas with a
. I
.normal tension. is to securely fasten the bobbin thread and to prevent
the stitches from loosening. While the stitch is taken in the facing the
thread is held under normal tension until the. hook has discharged the
loop when the tension automatically is releaseCl, giving the thread which
holds the two layers together a very loose tension.
91. CAUTION: Do Not under any circumstances, loosen set
screws in gear 1024, Figure R, above indicated by arrow in the
illustration. We especially caution you on this, as to loosen gear 1024
· m~ans throwing the automatic tension release out of time, which
mechanism is properly timed when the machine is assembled in our
factory.
92. In case it does become necessary to time the automatic
;ens ion release, this timing is done by loosening .the screws in gear
1024. Adjustment is then made witH the results outlined in Paragraph
90 are obtained·. An approximate method of making this adjustment is
to note that when the take-up is at its highest point, the single lobe of
the cam on the ·end of shaft 1552 should be horizontal andagainst
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48 Page
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