BA 5200 EN 08/2010
5.9
Backstop
For certain requirements, the gear unit can be fitted with a mechanical backstop. The backstop permits
only the specified direction of rotation during the operation of the unit. The direction of rotation is marked
by a corresponding arrow on the input and output side of the gear unit.
The backstop is mounted oiltight on an adapter flange on the gear unit and integrated in its oilcirculation
system.
The backstop is fitted with centrifugally operated sprags. If the gear unit rotates in the prescribed direction,
the inner ring rotates with the sprag cage in the direction of shaft rotation, while the outer ring remains
stationary. From a specific speed up (disengagement speed) the sprags disengage from the outer ring.
In this operating condition the backstop operates wearfreely.
6
5
3
4
2
1
Fig. 9:
Backstop
1
Outer ring
4
Shaft
2
Inner ring
5
Cover
3
Cage with sprags
6
Residualoil drain
The stop direction can be changed by turning the cage around. If a change in stop direction is
required, Siemens should be consulted beforehand.
To avoid damaging the backstop or the gear unit, the motor must not be run adversely
to the stop direction of the gear unit.
Observe the notice fixed to the gear unit.
Before connecting the motor, determine the direction of rotation of the threephase current supply using
a phasesequence indicator, and connect the motor in accordance with the predetermined direction of
rotation.
5.10
Heating element
At low temperatures it may be necessary to heat the gear oil before switching on the drive unit or even
during operation. In such cases heating elements may be provided, depending on the order, that convert
the electrical energy into heat which is conducted to the surrounding oil. The heating elements are located
in protective tubes inside the housing, thus making it possible to replace them without draining off the oil.
Complete immersion of the heating elements in the oil bath must be guaranteed.
The heating elements are controlled by a temperature monitor which emits a signal when maximum and
minimum temperatures are reached.
Never switch the heating elements on, unless complete immersion of the heating rod
in the oil bath is ensured. Fire hazard!
If heating elements are installed afterwards the max. heating capacity (see Table 7) on
the outer surface of the heating element must not be exceeded.
