Overrunning Clutch; Gear Unit With Auxiliary Drive And Torque­limiting Backstop - Siemens FLENDER H SH Series Assembly And Operating Instructions Manual

5.14.2 Overrunning clutch

If the gear unit is fitted with an auxiliary drive in addition to the main drive, coupling is realized by an
overrunning clutch. This allows, when driving by the auxiliary drive, a torque transmission in one direction
of rotation, while there is "free­wheeling operation" when driven by the main drive.
The output shaft of the main drive will rotate in the same direction of rotation both if the drive is effected via
the main motor and via the auxiliary drive.
The overrunning clutch is mounted in an adapter flange and integrated in the oil circuit of the gear unit.
Maintenance and oil change take place simultaneously with maintenance and oil change of the main drive.
The overrunning clutch is provided with centrifugally operated grippers. If the main gear unit is rotating in
the specified direction of rotation, the inner ring will rotate together with the grippers, while the outer ring
remains stationary. From a certain speed of rotation, the grippers will lift off and the overrunning clutch will
operate without wear.
If the drive is effected by the motor of the auxiliary drive via the outer ring, the overrunning clutch will be
in "carrier operation", i.e. the main gear unit is turned over slowly in the chosen direction of rotation. At
the same time, the drive shaft of the main gear unit and, if a flexible coupling is used between main motor
and gear unit, possibly the main motor will rotate slowly along with it.
The main motor and the motor of the auxiliary drive should be interlocked electrically in such
a manner that only one of the two motors can be switched on.
When driving via the auxiliary drive, the drive shaft of the main gear unit will rotate along
simultaneously. This rotary motion must not be impeded. A brake arranged on the drive side
in the main drive must be released if the drive is effected via the auxiliary drive.
When filling the main gear unit with oil, start by supplying lubricating point 1 at the
intermediate flange with the oil quantity and oil grade specified on the rating plate.
Prior to startup, the overrunning clutch should be checked for proper function
according to item 7.2.4.
5.14.3 Gear unit with auxiliary drive and torque­limiting backstop
If a torque­limiting backstop is used on gear units with auxiliary drive (see item 5.9), the slide
torque will already have been set at the correct value during the manufacturing process;
resetting or checking during startup is not required.
For safety reasons, it is absolutely prohibited to change the slide torque since,
otherwise, the auxiliary drive can be destroyed with explosive effect due to
overspeeds.
Furthermore, after having stopped the main motor, there is the additional danger that
the load is not safely held in its position and can run in reverse direction at high speed.
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