Design & Function
DREHMO actuators are comprised mainly of motor, planetary gear arranged with a torque-bearing displacement worm, handwheel without changeover clutch, sensors for torque and position measurement and an integral control unit.
All parts of the planetary gear are arranged arround the centre column. Because of the fact, that there are always multiple teeth of the planetary gear mashing - in contrast to a normal spur gear - a very compact gear design with a high life time can be realized.
Gear principle
- Life-time lubrication
- Manual operation via handwheel, changeover mechanism not necessary
- no starting problems even at low temperatures
- long life-time for on-off duty as well as for modulating duty due to low pressure at surface of gear wheels in combination with minimum friction of the meshing gears and optimal lubrication
- mounting and operation in any position permitted
Motor operation
The motor (1) drives the eccentric gear (3) via the spur gear (2). The planet wheel (4) is pivoted on the eccentric which meshes into the inner gear of the sun wheel (16). Because of the different numbers of teeth on each wheel, a relative speed exists which is transformed by the driver plate (5) via the follower pins (17) which are mounted on the planet wheel (4). The driver plate (5) engages with the pinion shaft (15) by means of serrations.
Torque related switch off
The sun wheel (16) also possesses, besides the inner gear tooth system, an external gear tooth system, which meshes with the displacement worm (13). This displacement worm is fixed in its central position by means of pre-loaded springs (12). In case of an output torque exceeding the torque caused by the pre-loading of the springs, the worm is displaced out of its central position and operates the torque lever (14). At the sensing point (11) either torque limits are detected by switches, operated by adjustable cams or torque values are continuosly measured by an analogue electronic sensor.
Manual operation by handwheel
Changeover from motorized to manual operation is not necessary. During manual operation by handwheel, the forces were transmitted via the worm (13), the sun wheel (16) and the planet wheel (4) to the driver plate (5) and thence to the output-drive.
