A Lighting Device

Background of the Invention

The present invention relates to a lighting device for ionising surrounding air while producing light.

Air ionisers have been produced for many years, for example to clean surrounding air of suspended particulate matter.

Brief Summary of the Invention According to an aspect of the present invention, there is provided a lighting device for ionising surrounding air while producing light, said device comprising: a housing having a pair of electrical connectors at each of two opposing ends of said housing, a tubular outer wall and an aperture defined by said tubular outer wall; an electrode extending through said aperture; a fluorescent tube extending along the interior of said housing, said fluorescent tube having electrical connections to said two pairs of electrical connectors; a voltage generator located within said housing and having a first input connection connected to one of said electrical connectors at a first end of said housing, a second input connection connected to one of said electrical connectors at said second end of said housing, and an electrical output connection connected to said electrode, such that when electrical power is applied to said electrical connectors said voltage generator applies a relatively high voltage to said electrode while relatively low voltages are supplied to said fluorescent tube to cause it to fluoresce. According to a second aspect of the present invention, there is provided a lighting device, comprising: an electrical connector for fitting in a lamp socket; a fluorescent tube; a first electrode for ionising air; a second electrode for ionising air; and an ion generator circuit configured to receive a relatively low ac voltage from said connector and supply a relatively high negative dc voltage to said first electrode while supplying a relatively high

positive dc voltage to said second electrode.

Brief Description of the Several Views of the Drawings

Figure 1 shows a conventional fluorescent lighting fixture 101 comprising a fluorescent lamp 102;

Figure 2 shows the lamp 102 is shown after removal from the lamp holder 103, along with a device 201 embodying the present invention;

Figure 3 shows the device 201 fitted within the fluorescent lamp holder 103; Figure 4 shows a circuit diagram of the device 201 within the lamp holder 103;

Figure 5A shows a simplified cross-sectional view of the device 201 ; Figure 5B shows a more detailed cross-sectional view of end portions of the device 201 ; Figure 6 shows a cross-sectional view along the longitudinal axis of the device 201 ;

Figure 7 shows a circuit diagram for the high voltage generator 517 of Figure 5;

Figure 8 an alternative device 801 embodying the present invention; and

Figure 9 shows a circuit diagram of the high voltage generator 917 of the device 801.

Written Description of the Best Mode for Carrying out the Invention

Figure 1

A conventional fluorescent lighting fixture 101 comprising a fluorescent lamp 102 is shown in Figure 1. The lighting fixture 101 comprises a fluorescent lamp holder 103 having a main body 104 that contains electrical terminals for connecting to mains electricity, a ballast and a starter 105. At each end of the main body 104, the lamp holder has a respective socket 106,

107 which is used to support the ends of the lamp 102 and make electrical connections to it.

Figure 2 The lamp 102 is shown after removal from the lamp holder 103, along with a device 201 embodying the present invention. The device 201 has a similar shape and appearance to the lamp 102, and, specifically, it has a cylindrical tube 202 with a metal cap 203 and 204 at either end. In addition, it has a pair of electrical connectors at each of its ends that are configured to be located within respective sockets 106 and 107.

As may be seen in Figure 2, the device differs from the lamp 102 in that it has an electrode 205 extending through an aperture in the wall of the cylindrical tube 202.

Figure 3

The device 201 is shown fitted within the fluorescent lamp holder 103 in Figure 3. As will be described in detail below, the device 201 comprises a fluorescent iamp, but in addition it comprises a high voltage generator connected to the electrode 205. Consequently, when mains electricity is supplied to the lamp holder 103, the device 201 emits light from its fluorescent lamp and negative ions are generated at the tip of the electrode 205.

Figure 4 A circuit diagram of the device 201 within the lamp holder 103 is shown in Figure 4. The lamp holder 103 has a pair of terminals 401 and 402 configured to allow connection to mains electricity supply. The first terminal 401 is directly electrically connected to a first of two electrical connectors 403

and 404 at one end of the device 201 , and the second terminal is electrically connected to a first of two electrical connectors 405 and 406 at the opposite end of the device 201 via a magnet ballast 407, in the form of an inductor.

The second connector 404 at the first end of the device 201 is electrically connected to one side of the starter 105 and the second connector 406 at the second end of the device is electrically connected to the other side of the starter 105.

The fluorescent lamp of the device 201 operates in a similar manner to a conventional fluorescent lamp. Thus, when mains electricity is supplied to the terminals 401 and 402, the switch provided in the starter 105 initially closes allowing current to build up through the ballast 407, and filaments within the fluorescent tube. After a short period of time, the switch within the starter opens to stop current flow through the filaments, and, due to the effect of the magnetic ballast 407, a high voltage is provided across the terminals 403 and 405, (connected to either end of the fluorescent lamp) to start the lamp. After the lamp has started, the ballast limits the current through the device, and thus the voltage appearing across the terminals 403 and 405 of the device is correspondingly limited.

It should be understood that the lamp holder 103 has been described for the purposes of illustrating the operation of the device 201 in an existing lamp holder. However, the device 201 may also be located and operated within a lamp holder having an electronic ballast, or may be configured to operate in a rapid start lamp holder which does not include a starter switch but has a ballast configured to maintain a voltage supply to the filaments even after starting.

Figures 5A, 5B and 6

A simplified cross-sectional view of the device 201 is shown in Figure

5A, a more detailed cross-sectional view of end portions of the device is shown in Figure 5B, and a cross-sectional view along the longitudinal axis of

the device 201 is shown in Figure 6.

The electrical connectors 403 and 404 are rigidly fixed within an electrically insulating disc 501 mounted within a cylindrically shaped metallic end-cap 203. The end-cap 203 has an inwardly extending lip at one end, against which the insulating disc 501 is mounted.

The electrical connectors 405 and 406 are similarly rigidly fixed within an electrically insulating disc 503 mounted within a cylindrically shaped metallic end-cap 204.

A cylindrical glass tube 202 has each end bonded within a respect one of the end-caps 203 and 204. A circular aperture 506 is formed in the wall of the glass tube 202 through which extends the end portion of the electrode 205.

The tube 202, end-caps 203 and 204, and insulating discs 501 and

503 together form a housing along which extends a fluorescent lamp 508. Thus, the fluorescent lamp and glass tube 202 extend along substantially the same axis with an air gap existing between the outside of the fluorescent lamp and the inside of the glass tube.

The fluorescent lamp 507 comprises a glass envelope 508 having a cylindrical side wall and end walls 509 and 510 through each of which extend a pair of wires 511 and 512 providing electrical connection to respective filaments 513 and 514 located at each end of the glass envelope 508. An electrical connection is provided between each of the pair of wires 511 and a respective one of the connectors 403 and 404, and similarly an electrical connection is provided between each of the pair of wires 512 and a respective one of the connectors 405 and 406.

The inside surface of the cylindrical side wall of the fluorescent tube 507 is coated with a phosphor layer 515 as is known in the art. In the present embodiment the phosphor 515 is a full spectrum tri-phosphor powder.

The glass envelope 508 of the fluorescent lamp 508 contains low pressure mercury as in known in the art.

The inner surface of the glass tube 202 is also coated with a phosphor layer 516.

The device 201 also contains a high voltage generator 517 located with the end-cap 204. The high voltage generator has an output connection connected to the electrode 205, a first input connection connected to the terminal 403 at one end of the device by an insulated wire 518, and connected to the terminal 405 at the other end of the device by an insulated wire 519. The wire 518 extends along the gap formed between the outside of the fluorescent tube 507 and the inside of the glass tube 202. The electrode 205 is enclosed within an insulating layer except for a portion at its end that extends through the aperture 506 formed in the tube 202. (For the purposes of clarity, this insulating layer is not shown in the figures.) The electrode 205 has the form of a brush, comprising a plurality of fine conductive filaments, of a type found in existing ionisers. In the present embodiment, the fluorescent lamp 507 is provided with connectors 520 and end-caps 521, but in an alternative embodiment such connectors and end-caps are not included and electrical connections are made directly between the wires 511 and 512 and the connectors 403 to 406 of the device. During operation, the fluorescent lamp 507 functions like other fluorescent lamps, and therefore excited mercury atoms, in the glass envelope 508, emit ultra-violet photons which collide with the phosphor layer 515 causing it to fluoresce, emitting visible light. A portion of the light emitted by the phosphor 515 is absorbed by the phosphor 516 causing it to fluoresce, while other emitted light passes through the phosphor layer 516.

During operation, the outer tube 202 has the appearance of a conventional fluorescent tube, and the inner tube 508 and wire 518 are hidden by the diffusing effect of the phosphor 516.

In the present embodiment, the phosphor 516, coating the outer tube 202, is a normal fluorescent powder, but it is envisaged that in other

embodiments the outer phosphor 516 is of a different type so that the spectrum of emitted light is adjusted. For example, the phosphor coating the outer tube 202 may be of a type which emits a warm colour spectrum.

During operation, the voltage appearing at either end of the fluorescent tube 507 is supplied to the input connections of the high voltage generator 517 by the wires 518 and 519. From this applied voltage, the voltage generator 517 is configured to generate a high negative voltage at its output connection that is connected to the electrode 205, Thus, the filaments of the electrode 205 are held at this high negative voltage, and consequently air molecules near the tips of the filaments become negatively charged and are repelled from the electrode.

In an alternative embodiment the outer tube is formed of a plastics material, but in each embodiment the tube is made of a translucent material. In one embodiment the outer tube is translucent but not transparent, and has an inner surface configured to diffuse light emitted from the fluorescent lamp.

In an alternative embodiment the outer tube is coated with a non- fluorescing transparent coating which merely acts as a diffuser.

Figure 7

A circuit diagram of the high voltage generator 517 of Figure 5 is shown in Figure 7.

Mains electricity is supplied to the input terminals 701 and 702 of the voltage generator 517 by wires 518 and 519, as mentioned above with respect to Figure 5. An input resistor 703 is connected at one side to. the input terminal 701 and at the other to one side of a capacitor 704. The other side of the capacitor 704 is connected to one lead of an input diode 705 which has its second lead connected to the second input terminal 702. The diode 705 is arranged to allow a negative flow from the input terminal 702 to the capacitor 704.

A unidirectional G1V series semiconductor (sidac) 706 connects the resistor side of the capacitor 704 to one end of a primary winding of a

transformer 707; the other end of the primary winding being connected to the diode side of said capacitor. The transformer has more turns on the secondary windings than the primary so that voltages induced across the secondary winding are sufficiently high. A second diode 708 is connected in series with a second capacitor

709 across the secondary winding of the transformer 707. The junction of the diode 708 and capacitor 709 is connected to the electrode 205 via a resistor

710 which provides a high impedance to the output, thereby limiting the output current to safe levels if touched during operation. During operation, the first capacitor 704 charges up until a threshold voltage of the sidac 706 is reached. A current then surges through the sidac to discharge the capacitor 704, thereby producing a large current pulse through the transformer primary winding. Consequently, a high voltage pulse is induced in the secondary winding which charges up the capacitor 709 via diode 708. Thus, the electrode 205 is held at high negative voltages, of typically between -4000 and -6000 volts.

Figure 8

An alternative device 801 embodying the present invention is shown in Figure 8. The device 801 has all of the features of device 201 as described above. Thus, it comprises a cylindrical tube 802 with a metal cap 803 and

804 at either end. In addition, it has a pair of electrical connectors 805 at each of its ends that are configured to be located within respective sockets of a fluorescent lamp holder (such as that shown in Figure 2).

The device 801 , like the device 201 , has a first output electrode 806 extending through an aperture in the wall of the cylindrical tube 802.

However, unlike the device 201 , the device 801 also a second output electrode 807 extending through a second aperture in the wall of the cylindrical tube 802, spaced a short distance along from the first output electrode. Like the tube 202 of device 201 , tube 802 is made from glass and is

coated on its inner surface with a phosphor. A fluorescent tube electrically connected to the connectors 805 is located within tube 802 such that a gap is formed between the inside of tube 802 and the outside of said fluorescent tube. This gap provides a passageway for an electrical conductor (918 shown in Figure 9), in a similar manner to conductor 518 of device 201. This electrical conductor connects one of the electrical connectors 805 at one end of the device to a high voltage generator circuit (described below with reference to Figure 9) located within the opposite end of the device.

The high voltage generator circuit provides a high negative voltage to the first output electrode 806, and also provides a high positive voltage to the second output electrode 807. Consequently, negatively charged ions are emitted away from the first electrode 806, while positively charged ions are emitted from the second electrode 807.

Figure 9 A circuit diagram of the high voltage generator 917 of the device 801 of Figure 8 is shown in Figure 9.

The high voltage generator 917 is in most respects the same as high voltage generator 517. Therefore, it is configured to have a.c. (alternating current) electricity supplied from connector 805 to input terminals 901 and 902 by wires 918 and 919 (in a similar manner to wires 518 and 519 of device 201). An input resistor 903 is connected at one side to the input terminal 901 and at the other side to one side of a capacitor 904. The other side of. the capacitor 904 is connected to one lead of an input diode 905 which has its second lead connected to the second input terminal 902. The diode 905 is arranged to allow a negative flow from the input terminal 902 to the capacitor 904.

A unidirectional G1V series semiconductor (sidac) 906 connects the resistor side of the capacitor 904 to one end of a primary winding of a transformer 907; the other end of the primary winding being connected to the diode side of said capacitor. Like the transformer 707, the transformer 907

has more turns on the secondary windings than the primary so that voltages induced across the secondary winding are sufficiently high.

A first output diode 908A is connected in series with a second capacitor 909A across the secondary winding of the transformer 907. The junction of the diode 908A and capacitor 909A is connected to the electrode

806 via a resistor 910A which provides a high impedance to the output, thereby limiting the output current to safe levels if touched during operation. In a similar manner, a second output diode 908B is connected in series with a third capacitor 909B across the secondary winding of the transformer 907. The junction of the diode 908B and capacitor 909B is connected to the electrode 807 via a resistor 910B.

The high voltage generator circuit 917 operates in a similar manner to generator circuit 517. However, the high voltage pulse induced in the secondary winding of transformer 907 charges up the capacitor 909A via diode 908A, and also charges up capacitor 909B via diode 908B. Thus, the electrode 806 is held at high negative voltages, of typically between -4000 and -6000 volts, while electrode 807 is held at high positive voltages.