Patent GB-814398-A (GB)
Title: Improvements in or relating to window or wall ventilating fans
IPC: F24F13/16
Filed: 1955-11-25
Abstract: 814,398. Axial-flow fans. LISLE, W. G., DE. Jan. 3, 1957 [Nov. 25, 1955; Jan. 30, 1956], Nos. 33882/55 and 2922/56. Class 110 (1). [Also in Group X] A window, or wall, ventilating fan is provided with means for opening and closing the fan when the motor is switched on and off respectively, the means comprising an axially movable but non-rotatable closure member 9, spring means 36-39 tending to press the closure member into a position to close the fan inlet opening, means operatively associated with the closure member and actuated automatically when the motor is switched on to move the closure member axially into the open position against the spring means, the arrangement being such that when the motor is switched off the spring pressure exerted on the closure member acts in a direction to return the closure member into the closed position; As shown, the ventilator fan comprises a cylindrical casing 10 which is clamped within an opening in a wall, or window 5, by means of a threaded. ring 13 which is screwed on to a reduced threaded portion of the casing extending through the window opening. An electric fan motor B is suspended by a spider 2 within the casing 10, the closure disc 9 being connected, by the spring strips 36-39, to a weather plate 14 which is spaced from the casing 10 by rods 15 carrying protective rings 16, 17. The disc 9, urged closed by the springs 36-39, is movable towards the weather plate 14 to open the fan inlet opening by means of a push rod 19 which is displaceable axially within a tubular motor shaft 18 and carries, on its inner end, a centrifugal device A, its outer end engaging a socket 20 mounted on the centre of the disc 9. The centrifugal device A, enclosed by a removable cover 8, comprises two similar weights 21, 22 which are pivoted at 23 to the outer ends of the cross arm of a tubular T-piece 24 screwed to the shaft 18 adjacent its inner end. The free ends of the weights are pivoted to arcuate links 26, 27, the outer ends of which are connected to a bridge piece 28 secured to the inner end of the rod 19. The two weights 21, 22 are recessed on their inner faces at 25 to accommodate the T-piece 24 and the push rod 19 when the motor B is switched off, two tension springs 34 being connected between pins 32, 33 carried respectively by the links 26, 27, to urge the latter together and the rod 19 withdrawn inwardly. When the motor B is switched on, the weights 21, 22 open radially against the springs 34, the rod 9 being moved outwardly through the shaft 18 to open the closure disc 9 against the opposing force of the spring strips 36-39. Upon switching the motor B off the spring strips 36-39 and the springs 34 return the closure disc 9 and the weights 21, 22 respectively to their closed positions. The spring strips 36-39 are twisted so that when the disc 9 is opened, they tend to straighten out and turn the disc 9 slightly to prevent it from tilting about its centre. In an alternative arrangement one end of the core of a solenoid, which is switchable with the fan motor circuit, is connected to the closure disc 9 which is movable against the springs 36-39 as shown, or against springs incorporated within, or externally of, the solenoid. The latter may be mounted on the weather plate 14 or on the motor casing.