GB2134728A - Ceiling fan - Google Patents

Abstract

The fan's operation is remotely controlled by an infra red signal or the like has two receiver units (40, Fig. 2) angularly spaced around the rotational axis of the fan blades at approximately 180 DEG to one another. Each receiver unit is covered by a wide angle, substantially hemi-spherical lens (42) to collect and focus signals received onto one or other receiver unit so as to enable control by a signal from substantially any angular orientation. Also for safety reasons a ceiling fan has a control circuit (52, Fig. 4) for the regulation of the speed of rotation of the fan blade and that circuit is optically coupled to an electronic switch for controlling fan motor energisation so that the control circuit can be electrically isolated from the mains supply. Further to avoid humming or ringing noise from the fan motor 12 a ceiling fan has an electronic switch 50 for controlling motor energisation, that switch being switched between "open" and "shut" positions only at or substantially at 0 DEG or 180 DEG in the phase angle of the AC supply to the motor. The control of speed is therefore exercised by repeated energisation for a whole number of half cycles of the AC phase angle followed by de- energisation for a whole number of half cycles of the AC phase angle, variation in the numbers of half cycles of energisation and de-energisation controlling the speed of rotation of the motor. <IMAGE>

Description

SPECIFICATION Improvements in ceiling fans This invention relates to ceiling fans and in particular the control and operation of such fans.

The remote control of various items of electrical apparatus such as television receivers, sound reproduction equipment and home video recorders is well known. The control is exercised by an infra red signal directed at the item from a remote hand-held control unit. For this signal to be effective, there must be a direct uninterrupted path between the unit and the item. This is not normally a problem for items such as those noted above but for a ceiling fan which will normally be in or near the centre of a room, this could be a problem.

Accordingly, in one aspect, the invention aims to provide control from any part of the room.

According to the invention, there is provided a remotely controlled ceiling fan in which the fan has two receiver units controlling the operation of the fan for signals from a remote hand-held unit, the receiver units being spaced angularly around the rotational axis of the fan blade at approximately 1 800 to one another, and each receiver unit being covered by a wide angle, substantially hemi-spherical lens to collect and focus signals received onto the receiver element of the unit.

With such a fan, it is possible to provide remote control from any position within the room, the two receivers being operated in parallel so that receipt of a signal by one or other or both controls the operation of the fan.

The remote control signal can have a number of channels for control of a large number of discrete functions such as, for example, variable speed of the fan blades, on/off control therefor, direction of rotation of the blades, and control of lights associated with the ceiling fan such as on/off control of the lights and their brightness.

In conventional remote-controlled ceiling fans, the mains electrical supply drives the motor for rotating the fan blades and the rate of rotation is controlled by an electronic switch in series with the motor, that electronic switch being controlled by a control circuit powered from the live wire of the mains supply through suitable voltage reducing means. The base or neutral of the control circuit is directly joined to the neutral wire of the mains and this is entirely satisfactory provided the ceiling fan is correctly installed. Many ceiling fans are, however, installed by the househoider himself and in the event that the mains supply wires are connected up the wrong way around, the casing for the fan can end up being connected directly to the live wire, a situation which is obviously highly disadvantageous.

According to another aspect of the invention therefore there is provided a ceiling fan having a remotely-controlled fan speed comprising a control circuit for receiving a remote signal and controlling the operation of an electronic switch which controls the energisation for the mains supply, and therefore speed, of the motor for rotating the fan blades, the output of the control circuit being optically coupled to an input for controlling the electronic switch and the circuit being otherwise electrically isolated from the mains supply.

By using such an arrangement, only the motor need be connected directly to the mains supply and the control circuit and remainder of the fan can be isolated therefrom. Therefore, irrespective of the way in which the mains supply is connected to the motor, the fan and control circuit will not live and so a possible source of danger. The optical coupling provides the control of motor speed required without a direct electrical coupling. Also, the control circuit could be energised from the mains by means of a transformer to ensure electrical isolation from the high voltage mains supply.

The electronic switch for controlling the energisation of the electric motor can be a triac.

Thus, the control circuit can be used to vary the firing point or voltage during the AC cycle to vary the energisation by variation of the proportion of each AC cycle over which the motor is energised.

The triggering by the triac will however cause "ringing" in the AC circuit, that is to say relatively high speed oscillations superimposed on the AC cycle as a result of the sudden "on" or "off" switching of the current during an AC cycle. This "ringing" results in the production of an undesirable hum hoise from the motor and it is an object of the invention in a further aspect to avoid or reduce this.

Therefore, according to this further aspect of the invention, there is provided a ceiling fan comprising a control circuit for the energisation of the motor for the blades to control the speed of rotation for the motor, the motor energised in series with an electronic switch, the switch being switched between "open" and "shut" positions only at or substantially at 0 and 1 800 in the phase angle of the AC supply to the motor, the control of motor speed being exercised by repeated energisation for a whole number of half cycles of the AC phase angle followed by deenergisation for a whole number of half cycles of the AC phase angle of the AC supply, variation of the numbers of half cycles of energisation and deenergisation controlling the speed of rotation of the motor.

The motor can be controlled from a maximum speed when the energisation is continuous, or in other words, there are zero numbers of half cycles of de-energisation, to a minimum stationary condition when the de-energisation is continuous, or in other words there are zero number of half cycles of energisation. Between these positions, there is a variation in the speed of rotation.

By controlling the motor speed in this way, the hum from the motor can be kept to a minimum very low figure because all of the switching by the elecronic switch is at zero, or substantially zero, current and so the "ringing" effect can be largely eliminated.

A ceiling fan according to the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an elevational diagram of a ceiling fan according to the invention; Figure 2 is a plan diagram of part of the ceiling fan shown in Figure 1; Figure 3 is a circuit diagram for the drive for a conventional ceiling fan; Figure 4 is a circuit diagram for the drive for a ceiling fan according to the invention; Figure 5 is a graph illustrating the control of fan motor speed in a conventional ceiling fan; Figure 6 is a graph illustrating the control of fan motor speed in a fan according to the invention; and Figure 7 is a circuit block diagram for the control of fan motor speed in the manner shown in Figure 6.

The ceiling fan 10 according to one aspect of the invention shown in Figures 1 and 2 comprises a motor 12 formed of a stationary stator 1 4 and a rotatable motor 1 6. The motor is contained within a housing 1 8 open underneath near its axial centre through which the ends of the fan blades 20 are joined to the rotor 1 6.

The fan hangs down from a ceiling 24 on a stationary rod 26 to which the housing and stator are fixed and to which the rotor is journalled.

Attached to the lower end of the rod 26 is a switch and control housing 30 and optionally a lighting fixture 32 can hang down from the underside of that housing 30. The housing 30 contains electrical wiring and circuitry (not shown) to control the operation of the fan 10.

The operation of the fan, e.g. rotor speed, direction of rotation and so on are remotely controlled from a hand-held unit, not shown, by an infra red control signal. Such a manner of remote control is well known and needs no further explanation here. The housing has two receivers 40 (Figure 2) for the infra red signals which are positioned diagonally opposite one another relative the rod 26. Each receiver 40 is covered by a hemi-spherical lens 42 so that from any orientation one or both receivers will be activated by a signal from the hand-held unit. Thus, as best shown in Figure 2, the angle over which each receiver can have a signal focused on it by the respective lens 42 is about 1 800.

Figure 3 shows a conventional control operation for a ceiling fan motor 12. The motor is connected in series with a triac switch 50 across the AC mains supply L-N. A low voltage DC supply is provided from the mains supply to a control unit 52 by means of a diode 54 and voltage dropping resistor 56. The control unit is grounded to housing 30 and the neutral N of the mains supply. The control unit 52 controls the firing of the triac in a conventional manner as will be described below in connection with Figure 5 to control the power supplied to the motor and so its rotational speed.

In the event that the AC mains supply is incorrectly joined so that the live L and neutral N are reversed, the housing 30 will be directly connected to the live L and so anyone touching the fan whilst it is switched on risks electrocution.

This can be avoided by the use of the circuit forming another aspect of the invention and shown in Figure 4. Interposed between the control unit 52 and the triac 50 is an optical coupling unit 60 and the low voltage power supply for the control unit 52 is provided by a step-down transformer 62. Thus, in this way, complete electrical isolation of the control unit 52 from the AC mains supply can be achieved since there is no direct electrical connection on either side of the line 64.

The optical coupling can be by means of, for example, a light-emitting diode 66, e.g. galliumarsenide infra red emitting diode, and a lightsensitive receiver 68 such as a silicon bilateral switch. Thus, the firing signals for the tirac 50 from the control circuit 52 are converted to an optical signal which is received by the receiver 68 and reconverted back to an electrical signal to control the triac.

The conventional control of motor 12 speed by, for example, a circuit of the type shown in Figure 3 is illustrated in Figure 5. The triac 50 fires and becomes conducting at a selected point in the AC mains supply voltage, e.g. the point 70 in Figure 5.

Thus, the motor 12 is energised during the shaded area of each cycle of AC voltage shown By variation of the position of point 70 along the AC voltage cycle, the duration of energisation can be varied from zero to full so infinitely varying the speed of the motor.

Because of the inductive component in the motor load, the sudden switching on during each cycle does not provide a current in the ideal form of plot A of Figure 5. Instead, "ringing" occurs and is superimposed on the current flow to give an actual current supply as shown in plot B of Figure 5. This ringing or interference results in the production of a "hum" noise from the ceiling fan.

This hum can be reduced or largely avoided by controlling the motor in the manner shown in Figure 6. Switching "on" or "off" by the triac 50 is always at a 0 or 1 800 position on the AC voltage cycle at which instant there is littie or no current flow. This largely avoids the ringing, and control of motor speed is achieved by repeatediy energising the motor, i.e. keeping the triac conductive, during a number of complete "half cycles" of the AC mains supply and shutting of the supply to the motor, i.e. keeping the triac non-conductive, during a further number of complete "half cycles" of the AC mains supply. By varying the proportion of these complete half cycles, the speed of the motor can be varied.

The plot D in Figure 6 shows the situation at full power and speed. the motor is energised for all "half cycles" and shut-off for zero half cycles. Plot E shows a medium power and speed. Here, the motor is supplied for ten half cycles followed by shut-off for the next ten half cycles. This continues repeatedly. Plot F shows a low power and speed, with repeated supply for four half cycles followed by shut-off for sixteen half cycles.

Control of speed can be achieved in this manner substantially without "hum" noise from the ceiling fan.

The block diagram shown in Figure 7 illustrates one form of control circuit for the triac 50 for controlling the speed of the fan motor 12 in the manner described in connection with Figure 6. In the diagram of Figure 7, there is a direct electrical connection between the control circuit and the triac 50 but this is not essential and instead there could be optical coupling as described in connection with Figure 4.

The control of speed is achieved by varying the value of adjustable resistors 80 and 82 and the voltage at the point 84 is compared with the steady voltage at point 86 between resistors R1 and R2 in a comparator 88. The output from the comparator controls a logic circuit 90 synchronised with the AC mains supply L-N by a synchronisation circuit 92 through the resistor R3.

The logic circuit determines the periods over which the triac 50 is conductive to give the result described in connection with Figure 6 through an amplifier 94.

Claims (10)

1. A ceiling fan comprising a control circuit for the energisation of the motor for the blades to control the speed of rotation for the motor, the motor being energised in series with an electronic switch, the switch being switched between "open" and "shut" positions only at or substantially 0 and 1 800 in the phase angle of the AC supply to the motor, the control of motor speed being exercised by repeated energisation for a whole number of half cycles of the AC phase angle followed by de-energisation for a whole number of half cycles of the AC phase angle of the AC supply, variation of the numbers of half cycles of energisation and de-energisation controlling the speed of rotation of the motor.

2. A ceiling fan as claimed in Claim 1 in which the switching of the electronic switch is controlled by a logic circuit synchronised with the AC supply to the motor, the logic circuit being in turn controlled from a speed-set signal.

3. A ceiling fan as claimed in Claim 2 in which the speed-set signal is derived from a comparator fed with a substantially fixed voltage and an adjustable voltage derived from the tap of an adjustable resistor.

4. A ceiling fan as claimed in Claim 2 or Claim 3 in which the coupling between the logic circuit and the electronic switch is an optical coupling.

5. A ceiling fan having a remotely-controlled fan speed comprising a control circuit for receiving a remote signal and controlling the operation of an electronic switch which controls the energisation from the mains supply, and therefore speed, of the motor for rotating the fan blades, the output of the control circuit being optically coupled to an input for controlling the electronic switch and the circuit being otherwise electrically isolated from the mains supply.

6. A ceiling fan as claimed in Claim 5 in which the control circuit is energised from the mains supply by means of a transformer to ensure electrical isolation from the high voltage mains supply.

7. A ceiling fan as claimed in any preceding claim in which the electronic switch is a triac.

8. A ceiling fan as claimed in any preceding claim which is a remotely controlled ceiling fan in which the fan has two receiver units controlling the operation of the fan for signals from a remote hand-held unit, the receiver units being spaced angularly around the rotational axis of the fan blades at approximately 1 800 to one another, and each receiver unit being covered by a wide angle, substantially hemi-spherical lens to collect and focus signals received onto the receiver elements of the unit.

9. A remotely controlled ceiling fan in which the fan has two receiver units controlling the operation of the fan for signals from a remote hand-held unit, the receiver units being spaced angularly around the rotational axis of the fan blades at approximately 1 800 to one another, and each receiver unit being covered by a wide angle, substantially hemi-spherical lens to collect and focus signals received onto the receiver element of the unit.

10. A ceiling fan substantially as herein described with reference to Figures 1 and 2, Figure 4, or Figures 6 and 7, of the accompanying drawings.