Operating Manual 90° ACTUSAFE CMF(S)QT
OM-ENGLISH-Failsafe-QT-16xx-V2.00-2022.03.01
3 Functional Description of the CMF(S)QT - Failsafe Drive
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Functional Description of the CMF(S)QT - Failsafe Drive
In normal operation, the actuator is operated by a motor (1). Via a worm gear stage (2) and a planetary gear train (3),
the motor drives the spindle nut of a ball screw (4). The sun gear shaft of the planetary gear train is fixed by an operating
current brake (5).
The ball screw converts the rotational movement of the gear unit into linear motion. On the one hand the linear movement,
charges the spring (7), which acts as an energy storage device. On the other hand, a rack-and-pinion gear (6) converts the
linear motion into the 90° output motion to move the fitting shaft (9).
There are no engaging or disengaging elements between the motor, the energy storage device and the fitting shaft in the
actuator. All the gear unit components are permanently engaged.
While moving against the Failsafe direction, the electric motor has to move both the fitting and the energy storage device
(spring) for the Failsafe stroke.
If the supply for the operating current brake is interrupted (by a power failure, or intentionally to trigger a Failsafe stroke, the
actuator will no longer be held, and the potential energy stored in the spring will be converted into kinetic energy to move
the actuator and thereby the fitting to the Failsafe position. In this case, the entire gear chain for the actuator except of the
worm gear stage will be moved until the adjustable, mechanical end stop (8) is reached or, if applicable, the stop for the
fitting.
Owing to this operating principle, neither an initialising stroke nor resetting of the actuator is required after a Failsafe stroke.
As soon as the power supply is restored, the actuator is immediately ready for operation.
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Figure 2:
1. . . Motor, 2. . . Worm gear stage, 3. . . Planetary gear train, 4. . . Ball screw, 5. . . Operating current brake,
6. . . Rack-and-pinion gear, 7. . . Spring , 8. . . End stop, 9. . . Fitting shaft
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