| 摘要 |
1. A fan comprising blades which can be automatically rotated about a longitudinal axis on an impeller hub of the fan, in order to avoid undesired rotation speeds, using centrifugal weights and two stop means, which are operative in different directions, characterized by the following features : a) first blades (2) are permanently arranged on the impeller hub (1) and the remaining blades (3) are mounted so as to be freely rotatable about their axes of gravity ; b) a first stop means (6) is provided which delimits the operating position of the remaining blades (3) and a second stop means (7) is provided against which the remaining blades (3) abut, in the event of a malfunction, in a position opposing the first blades (2) ; c) in an upstream region of the impeller hub (1) each of the remaining blades (3) is permanently connected to a counter-weight (5) ; d) at low starting speeds the remaining blades (3) are maintained solely by the counter-weight (5) - and at normal operating speeds additionally by the aerodynamic forces - in an operating position which is equivalent to the position of the first blades (2) (Fig. 1 to 4). |
