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