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Contact
- Free Overrun Clutches |
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Please
click image to order a catalogue.
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| These
are basically similar to conventional
sprag clutches, but the sprags
have their centre of gravity
offset to the pivot point such
that in the overrun mode the
sprag elements are thrown out
of contact with the stationary
race by centrifugal force These
clutches are for applications
involving long periods of high
speed freewheeling, when no
wear occurs, such as barring
motors, starter drives, pump
and motor backstops. Three basic
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Types RSBI and RBI
Types RSBI and RBI backstop
clutches consist of cylindrical
inner and outer races between
which are located individually
spring loaded, special shape
sprag elements contained in
a cage. The cage is flexibly
connected to the inner race
to allow the sprags to engage
easily during torque application.
When the inner race rotates
at high speed the off-centre
weight of the elements causes
them to rotate within the cage
to produce a gap with outer
race.
These clutches are designed
for backstop applications on
the high speed shafts of motors,
gearboxes, compressors and pumps.
They can also be used within
slow speed barring drive. Although
basically these clutches require
no lubrication, their sprag
design does permit the use of
E.E or H.E additives.
Type RSBI is dimensionally equivalent
to many competitor units; type
RBI offers higher torque capacity.
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Types RAZ and RIZ
Types RAZ and RIZ freewheel
clutches combine an RSBI sprag
cage unit with cylindrical inner
and outer races dimensionally
equivalent to same reference
AGF roller ramp freewheel. The
outer race is supported on two
60 series ZZ sealed bearings.
A range of flanges of same dimensions
as AGF series enables fitting
of gears, sprockets or pulleys,
and units with keyseated outer
race can also be provided.
Type RAZ clutches have sprag
clutch cage connected to outer
race to enable high speed overrunning
of the outer race. This series
mainly used for overrun applications
such as starter drives and barring
motors. Type RIZ clutches have
sprag clutch cage flexibly connected
to the inner race to enable
high speed operation of the
inner race. Whilst also suitable
for overrun applications, more
often this series is used as
backstop.
Both RAZ and RIZ clutches are
available with elastomeric coupling
as used with AGF series, with
RIZ being preferable as these
allow whole unit to be stationary
during overrun. |
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Types CR and RS/BF
Both types CR and RS/BF can
only be used as backstops, and
are normal1y mounted on rear
of electric motor, or on shaft
extension of gearbox. Special
shaped sprags are mounted in
a cage connected to the outer
race, which is of top hat shape
to enable connection to rotating
shaft. The inner race is flanged
to enable connection to machine
frame. The two series were originally
produced by two different companies,
and both have remained in production
as they are dimensionally different.
The units were the only selection
for contact-free backstops,
but now the RSBI and RBI series
are preferred for new applications.
The CR series units offer the
highest torque capacity with
300mm bore units capable of
75,000 Nm torque. Special clutches
have been supplied with torques
in excess of 150,000 Nm.
Both series have covers available
to provide a fully sealed unit.
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