GB2033491A

GB2033491A - Fans

Info

Publication number: GB2033491A
Application number: GB7933178A
Authority: GB
Original assignee: MYSON GROUP MARKETING Ltd
Current assignee: MYSON GROUP MARKETING Ltd
Priority date: 1978-09-26
Filing date: 1979-09-25
Publication date: 1980-05-21

Abstract

A fan comprises a drive shaft (10), a hub (12) mounted for rotation relative to the shaft (10) fan blades (14), each of which is mounted on the hub for pivotal movement between an inoperative first pitch position blocking the fan duct and an operative second pitch position, and drive means (17 to 20) which in addition to transmitting a rotary drive from the drive shaft (10) to the hub (12) pivots the blades (14) from their inoperative to their operative positions. <IMAGE>

Description

SPECIFICATION Fans The present invention relates to fans and is particularly, although not exclusively, concerned with fans used for ventilating purposes.

The fans hitherto proposed for ventilating purposes have been provided with blades set at fixed pitch angles and while these fans are effective for creating an airflow through an opening they have the disadvantage that when the fan is switched off and the blades at rest unwanted draughts are caused by air flowing through the gaps between the blades.

Various proposals have been made to overcome this disadvantage including the use of manually operable louvres to close the air duct within which the fan is installed when the fan is switched off, and the use of closure flaps which are displaced by the airflow created by the fan and which upon switching off the fan return to a position in which they close the air duct. These proposals have the disadvantage that a fitting additional to the fan assembly is required.

According to the present invention there is provided a fan comprising a drive shaft mounted for rotation, a hub mounted for rotation relative to the drive shaft, a plurality of fan blades, each of which is mounted on the hub for pivotal movement between an inoperative first pitch angle position and an operative second pitch angle position, and drive means which in addition to transmitting a rotary drive from the drive shaft to the hub pivots the blades from their inoperative positions to their operative positions.

Preferably the blades are pivoted from their inoperative positions to their operative positions against biasing means which restore the blades to their inoperative positions when the drive imparted by the drive shaft is removed.

The blades in the preferred embodiment of the invention preferably have zero pitch angles or substantially zero pitch angles and are of such a shape and size and so disposed that in their inoperative positions they provide no gaps or substantially no gaps between their adjacent edges, thereby to form a closure for a duct in which the fan is mounted.

In the preferred embodiment of the invention, the drive means comprises driving means on the drive shaft, driven means on the hub and blade pivoting means on the blades, whereby upon rotation of the drive shaft the driving means engages the blade pivoting means to cause pivoting of the blades from their inoperative positions to their operative positions, whereupon the blade pivoting means engages the driven means on the hub and transmits to the hub the rotary drive from the drive shaft.The biaing means then preferably comprises a spring connected between the shaft and the hub, whereby the rotary drive from the drive shaft in imparting pivotal movement to the blades tensions the spring, which upon removal of the drive from the drive shaft rotates the hub relative to the drive shaft and by engagement of the driven means thereon with the blade pivoting means causes the blade pivoting means to return the blades to their inoperative positions.

Preferably, the hub is mounted on the drive shaft for rotation relative thereto about'an axis coaxial with the drive shaft axis, each fan blade is carried by a stub shaft rotatably mounted in the hub and passing therethrough the blade pivoting means comprises an arm for each blade fixed to and extending radially from the stub shaft, the driving means on the shaft comprises a driving disc fixedly and coaxially mounted on the drive shaft and for each blade a pin eccentrically mounted on the driving disc and the driven means on the hub comprises for each arm a stop mounted on the hub, the arrangement being such that upon rotation of the drive shaft in one direction the pin for each blade engages and turns the arm causing pivotal movement of the blade from the inoperative position to the operative position, whereupon the arm engages the stop on the hub and transmits from the drive shaft to the hub a rotary drive in one direction. The arm for each blade in the preferred embodiment of the invention extends on each side of the stub shaft, the driving means comprises a further driving disc fixedly and coaxially mounted on the shaft and for each blade a further pin eccentrically mounted on the further disc, whereby rotation of the drive shaft in the opposite direction causes the further pin for each blade to engage the other end of the arm, causing pivoting of the blade from the inoperative position to the operative position, whereupon the arm engages the stop on the hub and transmits from the drive shaft to the hub a rotary drive in the opposite direction.

The following is a more detailed description of one embodiment of the invention, by way of example, reference being made to the accompanying drawings in which: Figure 1 is an end elevation of a six-bladed fan according to the invention, showing part of only one of the blades, with the drive motor stopped and the blades in a position of zero pitch.

Figure 2 is a cross-sectional side elevation of the fan shown in Fig. 1, the section being taken on the line ll-ll in Fig. 1.

Figure 3 is a cross-sectional side elevation of the fan shown in Fig. 1 similar to that shown in Fig. 2, with the blades pitched and rotating in the direction of the arrow A, Figure 4 is a further similar cross-sectional side elevation of the fan shown in Fig. 1, with the blades pitched and rotating in the direc tion of arrow B.

Referring first to Figs. 1 and 2, the fan comprises a drive shaft 10 mounted in bearings for rotation by a reversible motor 11 about the shaft axis. A hub 1 2 surrounds the drive shaft 10 and is rotatable relatively to the drive shaft 10 in bearings 1 3 carried by the drive shaft 10.

Six fan blades are equi-angularly spaced around the periphery of the hub, but for ease of illustration and description only one blade 14 is shown and its operation described, the others being identical and operated in a manner identical to that of the blade 14.

As best seen in Fig. 1, the fan blade 1 4 is carried on the end of a stub shaft 1 5 rotatably mounted in and passing through the hub 12, so that it can be pivoted with the stub shaft 1 5 about an axis normal to the common rotary axis of the drive shaft 10 and the hub 12. The end of the stub shaft 1 5 within the hub 12 has secured thereto a lever arm 1 6 which, in the position shown in Figs. 1 and 2, lies parallel to but spaced from the drive shaft 10 and is normal to the stub shaft 1 5.

The drive shaft 10 has fixedly mounted thereon two axially spaced discs 1 7 and 18 which carry on their peripheries radially extending pins 1 9 and 20 which cooperate with the lever arm 1 6 of the blade 14. Further pairs of pins (not shown) are likewise provided on the discs 1 7 and 18 for cooperation with the lever arms carried by the stub shafts of the other five blades (not shown). In the position shown in Fig. 2, the pin 1 9 on the underside of the disc 1 7 engages one end of the lever arm 1 6 on one side thereof and the other pin 20 on the underside of the disc 18 engages the other end of the lever arm 1 6 on the side thereof opposite to the side engaged by the pin 19.

The interior of the hub 1 2 is provided with a stop 21 for engaging the lever arm 1 6 in a manner described hereinafter. A further stop (not shown) is provided for each arm of the other blades. As best seen in Fig. 1, a coil spring 22 has one end thereof connected to the hub 1 2 and the other end thereof connected to a pin 23 carried by the disc 1 7 fixed on the shaft 10. The operation of the coil spring 22 will be described below.

In use, the fan is mounted inn an airflow duct (not shown) so that the blades in the zero pitch disposition shown in Figs. 1 and 2 form a closure for the duct.

In operation, the reversible motor is switched by a switch (not shown) to rotate drive shaft 10 in the direction indicated by the arrow A in Fig. 3. On initial rotation of the drive shaft 10 from the stationary position shown in Fig. 2, the pin 20 on the disc 18 engages the lever arm 1 6 and causes the arm 1 6 to turn clockwise as viewed in Fig. 2 and pivot the fan blade 14 out of the zeoro pitch disposition shown in Fig. 2 toward the disposition shown in Fig. 3. Since there is at this stage no rigid connection between the drive shaft 10 and the hub 12, the pivoting of the fan blade 14 will continue until the lever arm 16 engages the stop 21 on the interior surface of the hub 12 as shown in Fig. 3.At this pitch angle, the fan blade 1 4 is operative for driving air in the direction of the arrow C in Fig. 3, the drive of the motor 11 then being transmitted through the drive shaft 10, disc 18, pin 20, lever arm 16, and stop to the hub 1 2 to rotate the hub 1 2 and operate the fan.

The rotation of the drive shaft 10 relatively to the hub 1 2 tensions the coil spring 22.

When the motor 11 is switched off, the drive shaft 10 and the hub 12 will come to rest.

The tension in the spring 22 then operates to rotate the hub 1 2 about the shaft 10 and return the fan blades to their zero pitch dispositions as shown in Fig. 2, in which they form a closure disc closing or substantially closing the air duct.

When the direction of rotation of the motor 11 is reversed, the blade 14 is, as shown in Fig. 4, pivoted in the same direction and to the same pitch angle by the pin 1 9 of the disc 1 7 acting on the lever arm 1 6. In this case, the pin 19 on the disc 1 7 rotates in a direction opposite to the direction of rotation of the pin 20 on the disc 18, but engages the other end of the lever arm 16, with the result that the arm 1 6 turns again clockwise and causes the blade 14 to take up the same pitch dipositions as before when the arm 16 engages the stop 21. The drive shaft 10 then drives the hub 1 2 and the blades 14 rotate in the opposite direction to drive air in the direction of the arrow D in Fig. 4. The relative movement between the drive shaft 10 and the hub 1 2 loads the spring 22 in the opposite direction and when the motor 11 is switched off, the spring 22 returns the fan blade 14 to the inoperative position shown in Fig. 2.

In will be appreciated that if the motor is rotatable in one direction only, there may be provided only one disc and only one pin for each blade 14. It will also be appreciated that the blade 14 and the lever arm 1 6 may be other than at right angles to provide an alternative inoperative position of the blade 14.

Claims

1. A fan comprising a drive shaft mounted for rotation, a hub mounted for rotation relative to the shaft, a plurality of fan blades, each of which is mounted on the hub for pivotal movement between an inoperative first pitch angle position and an operative second pitch angle position, and drive means which in addition to transmitting a rotary drive from the drive shaft to the hub pivots the blades from the their inoperative positions to the operative position.

2. A fan according to claim 1, wherein the blades are pivoted from their inoperative posi tions to their operative positions against biasing means which restore the blades to their inoperative positions when the drive imparted by the drive shaft is removed.

3. A fan according to claim 1 or 2, wherein the drive means comprises a driving means on the drive shaft, driven means on the hub and blade pivoting means on the blades, whereby upon rotation of the drive shaft the driving means engages the blade pivoting means to cause pivoting of the blades from their inoperative positions to their operative positions whereupon the blade pivoting means engages the driven means on the hub and transmits to the hub the rotary drive from the drive shaft.

4. A fan according to claim 3, as appendant to claim 2 wherein the biasing means comprises a spring connected between the shaft and the hub, whereby the rotary drive from the drive shaft in imparting pivotal movement to the blades tensions the spring, which upon removal of the drive from the drive shaft rotates the hub relative to the drive shaft and by engagement of the driven means thereon with the blade pivoting means causes the blade pivoting means to return the blade to their inoperative positions.

5. A fan according to claim 3 or 4, wherein the hub is mounted on the drive shaft for rotation relative thereto about an axis coaxial with the drive shaft axis, wherein each fan blade is carried by a stub shaft rotatably mounted in the hub and passing therethrough, wherein the blade pivoting means comprises an arm for each blade fixed to and extending radially from the stub shaft, wherein the driving means on the shaft comprises a driving disc fixedly and coaxially mounted on the drive shaft and for each blade a pin eccentrically mounted on the driving disc and wherein the driven means on the hub comprises for each arm a stop mounted on the hub, the arrangement being such that upon rotation of the drive shaft in one direction the pin for each blade engages and turns the arm causing pivotal movement of the blade from the inoperative position to the operative position, whereupon the arm engages the stop on the hub and transmits from the drive shaft to the hub a rotary drive in one direction.

6. A fan according to claim 5, wherein the arm for each blade extends on each side of the hub shaft, wherein the driving means comprises a further driving disc fixedly and coaxially mounted on the shaft and for each blade a further pin, whereby rotation of the drive shaft in the opposite direction causes the further pin for each blade to engage the other end of the arm, causing pivoting of the blade from the inoperative position to the operative position, whereupon the arm engages the stop on the hub and transmits from the drive shaft to the hub a rotary drive in the opposite direction.

7. A fan according to claim 6, as appendant to claim 4, wherein the spring is such as to be tensioned by rotation of the drive shaft in either direction when pivoting the blades from their inoperative positions to their operative positions.

8. A fan according to any of the preceding claim, wherein the blades are of such a shape and size and so disposed that in their inoperative positions they provide no gaps or substantially no gaps between their adjacent edges, thereby to form a closure for a duct in which the fan is to be mounted.

9. A fan according to any of the preceding claims, wherein the blades in their inoperative positions have zero pitch angles or substantially zero pitch angles.

1 0. A fan assembly comprising a fan according to any of the preceding claims mounted in an air-flow duct, the blades in their inoperative positions closing or substantially closing the duct.

11. A fan substantially as hereinbefore described with reference to the accompanying drawings.