Fan and method for operating a fan

Abstract

The invention relates to a fan, particularly a radial fan, having a fan hub with a rotational axis. A plurality of fan blades is disposed about the rotational axis for deflecting an air flow. The invention provides that an adjustment device is provided at the fan blades for the rotational speed-dependant adjustment of an air flow.

Description

PRIOR ART[0001]The invention is based on a fan and a method for operating a fan as generically defined by the preambles to the independent claims.[0002]It is generally known in electric power tools to use fans, especially radial and semiaxial fans. Because of sometimes excessive idling rpm because of an overly low fan moment in idling, interfering vibration of the electric power tool can occur or be increased, which among other things reduces the brush service life of the electric motor and contributes to increased material fatigue.[0003]The fan in an electric power tool performs the task first of cooling the thermally stressed components in the electric power tool, and second, of regulating the idling rpm of the motor by means of a suitable idling moment. In a universal motor, for instance, by means of a fan disposed on the armature shaft, the universal motor is protected against uncontrolled revving during idling. A low load moment is also created by supporting the armature shaft ...

AI Technical Summary

Benefits of technology

[0018]Because of the lesser blade deformation at the operating point (that is, at a lesser rpm), there are a lesser flow deflection and a lower fan moment, and thus better efficiency of an electric power tool or electrical appliance in which the fan is disposed. As a result of the utilization of the fluid and centrifugal forces, which are always present, additional fittings, such as an active mechanical adjusting mechanism in the electric power tool or electrical appliance, can be dispensed with.

[0019]In the preferred passive variable-rpm blade deformation in preferred radial fans, for regulating the operating performance of electric power tools, an adaptation of the fan characteristic of the radial fan can advantageously be achieved by means of passive blade deformation, utilizing the incident fluid and centrifugal forces for optimizing the operating performance of electric power tools. In a favorable way, in the first alternative, the idling rpm can be reduced, and as a consequence, component vibration can be lessened. This also increases the brush service life in the AC range and postpones fatigue in the material. Noise emissions from the preferred electric power tool can be reduced as well.

Problems solved by technology

Because of sometimes excessive idling rpm because of an overly low fan moment in idling, interfering vibration of the electric power tool can occur or be increased, which among other things reduces the brush service life of the electric motor and contributes to increased material fatigue.

At the same time, noise emissions and the vibration load on the component structure both increase because of the high rpm.

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