GB1471492A - Ventilating fans - Google Patents

Abstract

1471492 Axial-flow fans VENT-AXIA Ltd 21 March 1975 [27 March 1974] 13666/74 Heading F1C [Also in Division F4] An axial-flow ventilating fan has pivoted overlapping shutters 23 for closing an annular air channel 11, and shutter operating means responsive to impeller rotation for moving the shutters to an open position when the impeller is rotating, the operating means comprises bob-weights 29 which move outwards by centrifugal force forcing a cone 33 to engage a ball race 38B on a plate 34, which moves axially against the compression in a spring 28, thereby permitting shuttles 27 to move to the left under the action of springs 27A and rotate shutters 23 to their open position. Plate 34 is freed from shuttles 27 when the latter engage a stop 36, further outward movement of bob-weights 29 causing a vane plate 31 and a race 31b to move to the right against the actions of a spring 31a, the race 31b engaging ball race 38A on a cap 39 which forms the abutment for spring 28 the cap thus being disengaged from stop 36 thereby relieving the motor shaft 15 from the spring thrust. When the impeller slows down, the operating means acts in reverse to close the shutters. To ensure positive movement of the shutters, a toggle mechanism comprising a movable pivot 23b and a leaf-spring 14c is provided.