Blind-fit Bellows Couplings
Linking motion with
less frustration
 Designing a coupling component into a motion system should
be fairly simple. You take into account parameters like rotational
speed, what sort of radius of turn (or radii of offset) is
expected, shaft size, ambient environment--all straightforward
requirements that can be handled by at least one off-the-shelf
assembly.
However, few couplings can readily cope with the real-world
issue of an axial motor change-out when the coupling is in
an inaccessible zone. In many circumstances, one maintenance
worker rotates the appropriate shaft while a second worker
peers into an access port, flashlight poised, watching for
the hub clamp screw to come into view.
Introduced at NDES in March 2001 was a German product that
will be sold stateside by satellite group R+W America, Glendale
Heights, IL. The design consists of a metal bellows with a
conical sleeve keyed to mate to a second mounting collar.
This sleeve is built of a glass fiber-enhanced plastic sprayed
onto a metal hub. The tapered construction of the plastic
component permits a smooth, self-adjusting press fit while
helping center the two shafts together, and the geometry of
the segment creates a backlash-free connection. The axial
pre-tension of the metal bellows also negates any backlash
to the driving and driven side, reducing bearing wear. An
added benefit of the plastic connection is its ability to
insulate between sides, both electrically and thermally.
The couplings are presently offered in two styles. The BK5
uses aluminum for the bellows face and the hubs, and a standard
clamping action to attach to shafting. The BK6 substitutes
steel for the aluminum, with axial clamping to accommodate
hard-to-reach installations. Stainless steel is used for the
bellows, and is an option for the faces and hubs. Depending
on model, rated torques range up to 500 Nm at speeds up to
50K rpm, making the couplings suitable for use with encoders,
tachometers, resolvers, and small servo drives in NC machine
tools and robotic drives. The units are rated to operate in
temperatures from -30° to 120°C.
--RM
For more information: Circle 555 - R+W North America
or connect directly to their website via the Online Reader
Service Program at http://www.OneRS.net/105df-555
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