Adding a second control tang to the output hub, along with a
stop collar, introduces a number of degrees of design freedom. For
example, this configuration can be used to implement a stop-start
clutch. The tang on the output hub engages with a stop collar or
stationary braking hub (see Figure 3). The collar can include multiple
stops. This configuration can also be used to prevent back driving or
limit travel to a single revolution.
A wrap-spring clutch/brake involves a second spring that connects the output hub to a stationary brake hub (Figure 4). The spring
includes a control tang. During a braking step, the clutch tang is used
to unwind the spring to disengage input and output hubs. At the same
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Figure 2: Adding a control tang to the input side of the spring converts
the basic design to a start-to-coast (random positioning) clutch/brake.
When the tang contacts the flange inside a stop collar on the input hub
side, it releases the spring and the load. (Image Credit: SEPAC)
Figure 3: Adding a stationary hub with a stop collar and a control tang
to the output hub converts the basic clutch design to a clutch/brake.
(Image Credit: SEPAC)