TSUBAKI EMERSON CAM CLUTCH

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B-4. BACKSTOPPING IN INTERMITTENT
FEEDING
Cam clutch and feed accuracy
When designing a high-accuracy feeding device that
incorporates Cam Clutch indexing, both the driving
and driven units must be made light in weight and high
in rigidity. Moreover, when selecting the ideal Cam
Clutch, it is extremely important to select a brake to
stop the driven unit at a preset position, a positioning
device, and a Cam Clutch for backstopping (which
cannot be expected of the Cam Clutch for indexing).
Feed accuracy = Cam Clutch for indexing +
Cam Clutch for backstop + Brake
Cam Clutch for backstopping
This Cam Clutch overruns
when the Cam Clutch for
indexing has completed one
feeding stroke. If the frictional
resistance of the driven unit
is smaller than the
overrunning frictional torque
of the Cam Clutch, or if a
reverse torque occurs on the
driving side due to back
MX Series
tension of the material, the
driven unit may rotate in reverse without stopping at
the end point fed by the Cam Clutch. The most
effective way to prevent this is to mount a Cam Clutch
for backstopping, although a brake or positioning pin
may also be used for this purpose. Since the Cam
Clutch for backstopping repeats the overrunning and
engagement at the same frequency as that of the Cam
Clutch for indexing, use one that is equivalent to the
feeding clutch or one that is one size smaller.
Brakes and other stopping devices
The outer race of a Cam
Clutch for indexing starts
reverse rotation immediately
upon the completion of one
feeding stroke. At the same
time, the Cam Clutch starts
overrunning. At this moment,
the driven unit is free from all
restrictions, and therefore,
when the driven unit has a
Cone brake
larger inertia or the feed
speed is faster, the inner race tends to rotate beyond
the stroke of the outer race. To prevent this, a friction
brake is often used as a braking device, although a
positioning pin or stopper may also be used for this
purpose. A braking device significantly improves the
feed accuracy. Accordingly, use a frictional brake which
has as small a fluctuation as possible in its braking
force. The wet-type cone brake is most effective. Please
consult TSUBAKI regarding brake selection.
B-5 FEEDING WITH STOPPER
(Feed frequency = Up to 300 times/min.)
(Feed angle = up to 90°)
In this application, a stopper forcibly stops the material
to be indexed at a position just before the feed end
point, to obtain a fixed feeding pitch. As soon as the
material hits the stopper, a shock torque larger than the
torque required for feeding is applied to the feeding roll
which is still rotating. The figure below shows an
example of a Cam Clutch used in a bolt header. The
wire is fed intermittently by a Cam Clutch mounted on
a grooved feed roll. Since the feed length of the wire is
set longer than necessary, the fed wire hits the stopper
which has been set at a position where the wire can be
fed at the necessary length. The reactive force this
generates acts as vibrating shock load upon the Cam
Clutch. It is therefore necessary to consider this when
selecting a Cam Clutch.
Example of bolt header
Applicable series
Consult TSUBAKI.
Cautions
When setting the feed length, consider the following:
Feed length setting = Necessary length + α
The closer to zero α is, the smaller the vibrating shock
load on the Cam Clutch becomes and consequently,
the longer the service life becomes.
www.bergab.ru Берг АБ bergab@ya.ru Тел. 17 (495)-228-06-21, факс (495) 223-3071