GB2136877A - Electric fans - Google Patents

Abstract

The fan comprises an assembly of three fans 60, each rotatable about its own axis and the entire assembly being rotatable about a vertical rod 19. A motor 62 rotates a friction plate in an assembly 3 and each fan is provided with a roller wheel so that when a respective knob of a clutch assembly 5 is rotated, the selected roller wheel is pushed into engagement with the friction plate thereby causing rotation of the fan blades. When a knob 6 is rotated, a rod (21 Fig. 3) engages teeth in an annular member (23) to cause the entire fan assembly to rotate. <IMAGE>

Description

SPECIFICATION An electric fan with multi-set blades able to rotate at 360e with precessional moment In summer days, the electric fan is one of our good companions; however, the conventional electric fan can only provide cool air at a limited angle. Fortunately, electric fans have been developed which can rotate 360 during blowing, such as those wherein the rotation at 360 is done by means of the fan motor, a worm and transmission mechanism. When the fan is rotating at low speed, the space within a given angle will have less wind in a unit of time; and when the fan is rotating at high speed, the transmission mechanism will generate noise, and the blowing is in an interrupted manner, with which the user would feel uncomfortable.A wide angle (360 ) fan can not provide cool air for a specific angle.

In view of the aforesaid drawbacks, the inventor has developed the present invention, an electric fan with multi-set blades able to rotate at 360" with precessional moment, in which multiple sets of fan blades are mounted on a connecting seat assembly spaced around the circumference at equal intervals. These multi-set fan blades may be driven by a rotary disk simultaneously or separately. If there are three sets of blades mounted on a circumference of 360 at equal intervals, the blowing force distribution around the circumference may be illustrated as shown in Fig. 10.

According to Fig. 10, the blowing force of fans is distributed at the angles of 30 , 150 and 270 while the connecting seat assembly is in a static condition. In order to let the angles of 90 , 210' and 230 have the same blowing force, the connecting seat assembly has to rotate at 360 by means of the precessional moment generated by the rotation of fans to drive the vertical axis to let the connecting seat assembly have a precession or a nutation.Since the angular speed of the precession is related to the rotation speed of fans and the friction force provided by the rotation control assembly, any variation of the friction force will vary the rotating speed of the connecting seat assembly, and will regulate the frequency of the variation of blowing force. In order to enable the fans to blow at a specific angle, the clutch assembly is furnished with clutch operation for the rotating assembly and the dynamic disk assembly, allowing all sets of the fan blades to rotate simultaneously or one set of fan blades or two sets of fan blades to rotate separately. Consequently, the electric fan of the present invention has a new structure and can provide a complete fan function.

A test sample of the present invention has been made, and its performance test has been proved to meet the functions required.

For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 is a perspective view of an embodiment of the present invention, which has three sets of fan blades; Figure 2 is a perspective view of the upper portion structure of the embodiment of this invention, which mainly illustrates the relationship and the structure among the fan rotating assembly 4, the dynamic disk assembly 3, and the fan clutch assembly 5; Figure 3 is a sectional view of line A-A in Fig. 2, i.e., the sectional view of the 360 rotation control assembly 6; Figure 4 is a perspective view of the clutch knob 1 3 in a fan according to the present invention;; Figure 5 is a sectional view of line B-B in Fig. 2, i.e., the sectional view of the fan clutch assembly 5; Figure 6 is a relationship view between the control rod seat 14 and the pull rod 1 5 in the fan clutch assembly 5 of the present invention; Figure 7 is a sectional view of line C-C in Fig. 1, illustrating the relationship among the dynamic disk assembly 3, the V-direction rotation speed control assembly 7, the lower fixing seat assembly 2, and the transmission shaft 44 of the present invention; Figure 8 is a perspective view of the second embodiment of the V-direction rotation speed control assembly of the present invention; Figure 9 is a perspective view of the rear portion of the fan rotating assembly 4 of the present invention; and Figure 10 is a graph of blowing force against relative blade positions.

The present invention, an electric fan with multi-set blades able to rotate at 360 with precessional moment, comprises the dynamic assembly 1, the lower fixing seat assembly 2, the dynamic disk assembly 3, the fan rotating assembly 4, the fan clutch assembly 5, the 360 rotation control assembly 6, the V-direction rotation speed control assembly 7, the motor speed control assembly 8, the upper fixing assembly 10, and the connecting seat assembly 61. The dynamic assembly 1 will be able to have the dynamic force transmitted, through the transmission shaft 44, to the dynamic assembly 3 (as shown in Fig. 7) for driving the engaged roller wheel 41 (as shown in Fig. 2) on the friction plate 33 so as to have the fans 60 of the fan rotating assembly 4 rotated in "W" direction.Upon the roller wheel 41 being disengaged from the friction plate 33, the fans 60 would not rotate. Between each fan rotating assembly 4 and the friction plate 33, there is a discrete clutch means, i.e., the fans 60 can rotate simultaneously or separately. The clutch means is controlled by the fan clutch assembly 5 by merely operating the clutch knob 1 3. The fan rotating assembly 4 is controlled by the 360 rotation control assembly 6 for 360 rotation. As shown in Fig. 3, when turning the knob 1 8 clockwise, the fan rotating assembly 4 will be unable to move circularly in "V" direction; and the fans 60 can only blow towards the front.Upon the knob 1 8 being tuned counterclockwise, the fan rotating assembly 4 will, around the supporting pole 1 9 as axis, move circularly in "V" direction so as to provide a comfortable blowing force of variation at every angle. The angular speed of "V" direction circular movement of the fan rotating assembly 4 is controlled by the V-direction rotation speed control assembly 7 or 9 as shown in Figs. 7 and 8. Fig. 7 illustrates an embodiment showing how the V-direction rotation speed of the fan rotating assembly 4 may be adjusted by varying the friction force of the gear assembly.

Fig. 8 illustrates a second embodiment showing how the V-direction rotation speed of the fan rotating assembly 4 may be adjusted by varying the friction force between the leaf spring 53 and the brake drum 52. The rotating speed of the dynamic assembly 1 is controlled by the motor speed control assembly 8, which divides the rotating speed of the motor into several stages. The upper fixing seat assembly 10 and the lower fixing seat assembly 2 are connected together by means of the screen frame 24. The lower fixing seat assembly 2 and the supporting pole 1 9 are fixed together; in other words, the upper fixing seat assembly 10 and the lower fixing seat assembly 2 are all fixed structures.

On the lower fixing seat assembly 2, the parts of the V-direction rotation speed control assembly 7 are installed. The connecting seat assembly 61 is used for assembling together the speed-down seat 42, the fan rotating assembly 4, the fan clutch assembly 5 and the 360 rotation control assembly 6 so as to have all of said means move circularly in "V" direction but maintaining their relative positions.

The dynamic assembly 1 comprises the motor 62, the supporting pole 19, the transmission shaft 44 and the bearing 45.

The supporting pole 1 9 is substantially a hollow steel tube, of which both ends are connected respectively to the case of motor 62 and the lower fixing seat 50 of the lower fixing seat assembly 2, forming a unit, The transmission shaft 44 is installed in the supporting pole 1 9 One end of the transmission shaft 44 is connected with the main axle of motor 62, while the other end, the top portion 44a, extends out of the supporting pole 19 from the bearing 45 portion as shown in Fig.

7 so as to have the dynamic force of motor 62 transmitted to the top portion 44a of the transmission shaft 44. The top portion 44a of the transmission shaft 44 is in a polygon shape so as to be engaged with the polygon stud 65 on the dynamic disk assembly 3 in order to have the dynamic force transmitted to the dynamic disk assembly 3.

Said dynamic disk assembly includes the rotary disk 32, the friction plate 33 and the polygon stud 65. The friction plate 33 is made of friction-proof material that has a high co-efficient of friction, such as leather or hard rubber, etc.; the friction plate 33 is firmly stuck to the rotary disk 32; the polygon stud 65 is installed in the center of the rotary disk 32, but is at the opposite side of the friction plate 33. Upon the dynamic force transmitted by the transmission shaft 44 driving the dynamic disk assembly 3 to rotate clockwise (or counter-clockwise), the axle 34 will rotate if the friction plate 33 and the roller wheel 41 on the fan rotating assembly 4 are contacting each other. If there are several roller wheels 41 to be installed on the circumference of friction plate 33, the same number of axles 34 may rotate as well to drive multiple fans 60.In such a structure, the noise and the wear and tear factors will be reduced to a minimum; in other words, the said structure of the present invention is much better than the worm and gear means or the bevel gear being used for transmission or rotation.

The fan rotating assembly 4 comprises the roller wheel 41, the axle 34, the bushing 35, the adjustable bearing 36, the fan 60, and the bearing 68. The end portion 34b of the axle 34 is fitted with a bearing 68, and then is fitted into the bearing block hole 30b of the bearing block 30. At the end portion 34a of said axle 34, an adjustable bearing 36 is installed; the extended portion of said axle is connected with the fan 60. The adjustable bearing 36 is installed in the bushing 35, which is fixed in position with the upper and lower supporting frames 28 and 40 so as to have both ends of the axle 34 firmly supported. Upon the bearing block 30 being pulled up, the roller wheel 41 will be disengaged from the friction plate 33 (the adjustable bearing 36 being the turning center).

Upon the bearing block 30 being released downwards, the roller wheel 41 will closely contact with the friction plate 33 as a result of its weight and the pressure spring 29. If the roller wheel 41 comprises a permanent magnet, the roller wheel 41 may closely contact the friction plate 33 by magnetic force; in that case, the lower seat 31, the bearing block 30, and the axle 34 should all be made of nonmagnetic material, and the rotary disk 32 should be made of magnetic material.

The fan clutch assembly 5 includes the clutch knob 13, the control rod seat 14, the pull rod 15, the control rod 16, the pin 17, the locking nut 20, the adjusting screw 25, the pressure spring 29, and the bearing block 30. Referring to Figs. 2, 4, 5, and 6, there is shown the bearing block 30 being mounted in the sliding groove 31 a of the lower seat 31 so as to make Y-direction movement. The adjusting screw 25 is used for adjusting the pressure of the pressure spring 29 to the bearing block 30 so as to regulate the pressure between the roller wheel 41 and the friction plate 33.One end of the adjusting screw 25 is locked together with the screw nut 1 sic of the pull rod 15, while the other end of said adjusting screw passes through the mid-seat 26 and the tongue piece 30a of the bearing block 30 so as to hang the bearing block 30 on the adjusting screw 25. One end 15b of the pull rod 1 5 extends into the concave position 1 4c of the control rod seat 14, and there is a clearance "d" so as to let the pull rod 1 5 move up.At the end 15b of the pull rod 15, there is an oblique groove 15a, of which the wider opening end is facing the pin 1 7. The clutch knob 1 3 is a two-cascade stud; and on the outer surface of its body 13b, there is a sliding groove 13a, in which the front end 1 6a of the control rod 1 6 is encased.Upon turning the clutch knob 13, the front end 1 6a of the control rod 1 6 may be slid to the upper portion 1 3d or the lower portion 1 3e in the sliding groove 13a; then, the control rod 1 6 is pivoted on the pin 1 7 to turn clockwise or counter-clockwise so as to have the pull rod 1 5 make Y-direction movement, and to provide a clutch relationship between the roller wheel 41 and the friction plate 33. The stud portion 1 3c inside the clutch knob 1 3 is matched with the positioning hole 1 4a of the control rod seat 14.Since the pull rod 1 5 extends in the concave portion 1 4c of the control rod seat 14, the control rod seat 14 will not turn together with the clutch knob 1 3. The portion of control rod 1 6 between its front end 1 6a and the pin 1 7 is shorter than that between its rear end 1 6b and the -pin 17; in such a manner, the pull rod 1 5 will have greater displacement upon the clutch knob 1 3 being turned slightly for controlling the clutch operation.

The 360 rotation control assembly 6 includes the knob 18, the mid-pole 63, the positioning bar 21, the pressure spring 70, and the tooth-shaped annular seat 23. The stem portion 1 8a of the knob 1 8 passes through the lid 1 2 and the upper seat 11, and extends inside the mid-pole 63, contacting with the pressure spring 70. The mid-pole 63 is a hollow steel pole, on the top of which there are a horizontal slot 63b and a vertical slot 63a being in communication with each other. The positioning bar 21 passes through the vertical slot 63a or the horizontal slot 63b to connect with the stem portion 18a.Referring to Fig. 3, there is shown the positioning bar 21 being put in the horizontal slot 63b to cause the fan rotating assembly 4 to move circularly in the "V" direction; upon the positioning bar:2la being in the vertical slot 63a, the pressure spring 70 will push the positioning bar 21a upwards to have the bar 21a retained inside the groove 23a of the toothshaped annular seat 23 so as to prevent the fan rotating assembly 4 from moving circularly in the "V" direction. The positioning bar 21 is controlled with the knob 18 for placing in the vertical slot 63a or in the horizontal slot 63b; as shown in Fig. 3, when the knob is turned clockwise, the bar 21 will be placed in the vertical slot 63a; when the knob is turned counter-clockwise, the bar 21 will slide into the horizontal slot 63b.The tooth-shaped annular seat 23 is firmly fixed in the inner diameter space of the upper fixing seat 22; on one side of the tooth-shaped annular seat 23, teeth 23b are furnished to form a groove 23a being wider than the diameter of the position ing bar 21. The mid-pole 63 and the upper seat 11 are firmly fixed together.

The V-direction rotation speed control assembly 7 is used for controlling the rotating speed of the speed-down seat 42. Referring to Fig. 7, there is an embodiment in which the V-direction rotation speed of the fan rotating assembly 4 may be adjusted by varying the friction force of the gear assembly. In Fig. 8, the friction force between the brake drum 52 and the leaf spring 53 may be adjusted by varying the angle of the wheel 57 to turn the eccentric wheel 55 so as to control the rotating speed of the speed-down seat 42. The speed-down seat 42 is in snug fit with the outer surface of the supporting pole 19; the top inside surface of said speed-down seat 42 rests on a flat bearing 43 so as to have the speed-down seat 42 turn around freely.

The main feature of the V-direction rotation of the fan rotating assembly 4 is, by means of the V-direction high rotation speed of the fans 60, to have all of the movable components (including the connecting seat assembly 61, the speed-down seat 42, the fan rotating assembly 4, the fan clutch assembly 5, and the 360 rotation control assembly 6) generate a precession, i.e., a "nutation". Therefore, the V-direction rotation needs no dynamic force transmission mechanism from the motor 62; that feature may be deemed as a big break-through in terms of technical concept.

The connecting seat assembly 61 includes the lid 12, the upper seat 11, the mid-pole 63, the mid-seat 26, the lower seat 31, the upper supporting frame 28, and the lower supporting frame 40; they are mainly used for connecting the components of the speeddown seat 42, the fan rotating assembly 4, the fan clutch assembly 5, and the 360 rotation control assembly 6. On the upper seat 11, there are installed the clutch knob 13 and the knob 18. The upper seat 11 and the mid-seat 26 are connected by means of the mid-pole 63. The mid-seat 26, the upper supporting frame 28 and the lower seat 31 are fixed together with the fixing screw 27.

The upper supporting frame 28 and the lower supporting frame 40 are fixed to the upper and lower portions of the bushing 35 respectively. The other end of the lower supporting frame 40 is connected to the speed-down seat 42; in other words, the whole mechanism is pivoted on the supporting pole 1 9.

According to the aforesaid description, the present invention, having a plurality of fans, can provide cool air by rotating separately and simultaneously, and can, by means of high rotation speed of the fans, generate a precessional moment to have the fan rotating assembly make a "precession". Consequently, the present invention can provide comfortable blowing force of variation at every angle around a circle. This technical concept is completely different from that of the conventional electric fan, and it is deemed as novel and practical. It will be understood of course that, while the form of the invention herein shown and described constitutes preferred embodiment of the invention, it is not intended to illustrate all possible forms of the invention.It will also be understood that the words used are words of description rather than of limitation and that various changes may be made without department from the spirit and scope of the invention, as defined by the claims appended hereto.

CLAIMS 1. An electric fan with multi-set blades, able to rotate at 360 with precessional moment, comprising a dynamic assembly, a lower fixing seat assembly, a dynamic disk assembly, fan rotating assemblies, fan clutch assemblies, a 360 rotation control assembly, a V-direction rotation control assembly, a motor speed control assembly, an upper fixing seat assembly, and a connecting seat assembly; wherein said dynamic assembly transmits dynamic force to said dynamic disk assembly which transmits the dynamic force to said fan rotating assembly to drive the multiple fan, the fans are mounted on a connecting seat assembly at equal intervals around a circle are controlled by the fan clutch assembly and are driven by a rotary disk separately or simultaneously; all said fans being able to rotate together with the connecting seat assembly at 360 , by means of the precession generated by the precessional moment during the fans rotating, to drive the connecting seat assembly, said 360 rotation control assembly controlling the amount of rotation of the fan rotating assembly and the connecting seat assembly, and the V-direction rotation speed control assembly controls the angular speed of 360 rotation of said fan rotating assembly and the connecting seat assembly.

2. An electric fan as claimed in claim 1, wherein the dynamic disk assembly comprises a rotary disk, a friction plate and a polygon stud; said friction plate being made of frictionproof material with high friction co-efficient; said friction plate being firmly adhered together with the rotary disk; the dynamic force being transmitted from the transmission shaft through the polygon stud to said friction plate, which may contact with the roller wheel on said fan rotating assembly so as to transmit the dynamic force to said roller wheel for driving the fans.

3. An electric fan as claimed in claim 1 or 2, wherein the fan rotating assembly comprises roller wheels, axles, bushings, adjustable bearings, bearings and the fans; said roller wheels being contacted with said friction plate on said dynamic disk assembly; said bearing being installed on the bearing block of said fan clutch assembly; said adjustable bearing being installed inside the bushing which is fixed with the upper and lower supporting frames; upon said bearing block being pulled upwards, said roller wheel will disengage from said friction plate; and upon said bearing block being released down, said roller wheel will again closely contact with said friction plate as a result of its weight and the pressure spring, and the fans will be driven.

4. An electric fan as claimed in claim 3, wherein, when the roller wheel is made of permanent magent, the other components, such as said lower seat, bearing block, and axle should be made of non-magnetic material, and the rotary disk should be made of magnetic material.

5. An electric fan as claimed in claim 1, 2 or 3 wherein the fan clutch assembly comprises clutch knobs, control rod seats, pull rods, control rods, pins, locking nuts, adjusting screws, pressure springs, and said bearing blocks; said bearing block being installed inside the sliding groove of said lower seat so as to move in "V" direction; said adjusting screw being used for adjusting the pressure of said pressure spring to said bearing block so as to regulate the pressure of said roller wheel to said friction plate; the end of said pull rod extending inside the concave portion of said control rod seat but maintaining a clearance "d"; at the end of said pull rod, an oblique groove being furnished, and the wider opening of said oblique groove facing the pin; upon said control rod and said pin being installed inside the control rod seat, the portion of said control rod from its front end to said pin being shorter than from its rear end to said pin; said clutch knob being a twocascade stud, and on the outer surface of its body, a sliding groove being furnished for encasing the front end of said control rod; and upon turning the clutch knob, said control rod may be pivoted on said pin to turn clockwise or counter-clockwise so as to have said pull rod move back and forth in "V" direction.

6. An electric fan as claimed in any preceding claim, wherein the 360 rotation control assembly comprises a knob, mid-pole, positioning bars, pressure spring, and the tooth-shaped annular seat; upon turning the knob, the positioning bar will be moved to change its position on said mid-pole, and when said positioning bar is in the horizontal slot, the fan rotating assembly will move circularly in "V" direction; upon said positioning bar being in the vertical slot, said pressure spring will push said bar upwards to have the bar retained inside the groove of said toothshaped annular seat to prevent said fan rotating assembly from moving circularly in "V" direction; and said tooth-shaped annular seat and the upper fixing seat are firmly fixed together.

7. An electric fan as claimed in any preceding claim, wherein the V-direction rotation speed control assembly mainly controls the rotating speed of speed-down seat by means of varying the friction force of the gear assembly to adjust the V-direction rotating speed of said fan rotating assembly.

8. An electric fan as claimed in claim 7, wherein the friction force between the brake drum and the leaf spring may be adjusted by varying the angle of the wheel to turn the eccentric wheel so as to control the rotating speed of the speed-down seat.

9. An electric fan as claimed in any preceding claim, wherein the connecting seat assembly is mainly to connect said speeddown seat, fan rotating assembly, fan clutch assembly, and said 360 rotation control assembly to form a whole movable mechanism for generating V-direction precession synchronously.

10. An electric fan with multi-set blades able to rotate at 360 with precessional moment substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

Claims (10)

1. An electric fan comprising: a support having a first axis; first and second fixing assemblies rotatably mounted on the support for rotation about the first axis; a plurality of fan elements each having one or more blade, each element being fixedly attached to the first and second assemblies and rotatable about a respective second axis of rotation, which axis is inclined with respect to the first axis; a disc assembly rotatably mounted on the support for rotation about the first axis; a respectively clutch assembly associated with each fan element by means of which each element may selectively be brought into contact with the disc assembly;; a drive means for causing rotation of the disc assembly, whereby, with one or more fan element in contact with the disc assembly, rotation of the disc assembly about the first axis causes the or each fan element in contact therewith to rotate about its respective second axis, such rotation of the or each fan element generating a torque which can cause the first and second fixing assemblies to rotate about the first axis, the fan further comprising a control means for controlling the angular speed of rotation of the first and second fixing assemblies about the first axis, and a stop means for selectively preventing the torque generated by the or each fan element from causing the first and second fixing assemblies to rotate about the first axis.

2. An electric fan as claimed in claim 1, wherein: the disc assembly comprises a rotatable disc having a layer of material with a high coefficient of friction; each fan element has a roller mounted for rotation about the second axis for contacting the material of the disc; and the drive means includes a shaft operatively connected to the disc assembly for rotating the same whereby the or each roller in contact with said material is caused to rotate thereby causing rotation of the respective fan element.

3. An electric fan as claimed in claim 1 or 2, wherein each clutch assembly comprises a bearing housing, slidably mounted to the first assembly for movement along a direction substantially parallel to the first axis, for receiving a bearing of a respective fan element.

4. An electric fan as claimed in claim 3, wherein each fan element further comprises: an axle for the roller, the axle carrying the bearing; and a bushing housing an adjustable bearing, and axle being disposed within the bushing, and the adjustable bearing being disposed between the bushing and the axle, the bushing being fixed with respect to the first and second fixing assemblies, the arrangement being such that, upon each bearing housing being caused to slide away from the disc, the associated roller will be brought out of contact with said material, and upon said bearing housing being caused to move towards the disc, said roller will contact the material to cause the respective fan element to rotate on rotation of the disc.

5. An electric fan as claimed in claim 4, wherein the roller is made of a permanent magnetic material, the disc is made of a magnetic material, and the axle and the bushing are made of a non-magnetic material.

6. An electric fan as claimed in claim 4 or 5, wherein each clutch assembly further comprises a respective biasing means and adjusting device associated with each bearing housing, wherein said bearing housing is slidably installed in a groove of the first assembly, and wherein the adjusting device is used to adjust the force exerted by the biasing means on the bearing housing so as to regulate the pressure of the respective roller on the material of the disc.

7. An electric fan as claimed in claim 6, further comprising a control assembly mounted on the support for rotation with the first assembly about the first axis wherein the clutch assembly further comprises a pull rod attached to the bearing housing, one end of which extends in a portion of a rod seat housed in a control knob of the control assembly, said one end being spaced from the adjacent end of the rod seat, the pull rod being provided with a transverse groove in the form of a truncated cone, with a wider opening of said transverse groove facing a pin disposed inside the rod seat, wherein a control rod is pivotally mounted on the pin, one end of the control rod being received by the transverse groove, and the other end of the control rod being disposed for movement in a further groove formed in a cylindrical surface of the control knob whereby rotation of the control knob causes the control rod to move in the further groove and consequently to pivot about the pin whereupon the one end of the control rod received by the transverse groove of the pull rod causes the pull rod to move along the direction of movement of the bearing housing to control movement of the bearing housing attached to the pull rod.

8. An electric fan as claimed in claim 7, wherein the stop means comprises a protrusion disposed on the control assembly, an elongate member attached to the protrusion and rotatable therewith, a sleeve disposed about the elongate member and being provided with a substantially L-shaped slot, a positioning bar fixedly attached to the elongate member and movable within the slot a second biasing means, and an annular member disposed around the support and fixedly attached to the control assembly, the annular means being provided on a face remote from the control assembly with projections, wherein, upon turning the protrusion the positioning bar can change its position relative to the slot, so that, with the positioning bar disposed within a horizontal leg of the substantially L-shaped slot, the control assembly and therewith the first and second positioning bar being in a vertical portion of the substantially L-shaped slot, the second biasing means will cause the pole to be urged in a direction so as to maintain the positioning bar in said vertical portion, in which position the bar is retained between projections of the annular member to prevent the control assembly and thereby the first and second assemblies from rotating.

9. An electric fan as claimed in any preceding claim wherein the control means comprises a brake drum around which is disposed a resilient element, an eccentrically mounted spacing element disposed between end regions of the resilient element and an operating means by means of which the spacing element can be rotated whereby the friction force between the drum and the resilient element may be adjusted by varying the disposition of the spacing element.

10. An electric fan substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.