WO2013021378A1

WO2013021378A1 - Bipolar ion generator with cleaning of ionizing electrodes

Info

Publication number: WO2013021378A1
Application number: PCT/IL2012/000296
Authority: WO
Inventors: Yefim Riskin
Original assignee: Yefim Riskin
Priority date: 2011-08-08
Filing date: 2012-08-07
Publication date: 2013-02-14
Also published as: IL214503A0; IL214503A

Abstract

A bipolar ion generator (100) configured for automatic cleaning of ionizing electrodes, includes a pair of deflectable ionizing electrodes (6, 7) coupled to a source of high voltage (14) and configured for rotation about a rotation axis by a variable speed electric motor (3). A stationary cleaning unit (19) is mounted in spatial disposition with the ionizing electrodes (6, 7) and separated therefrom at normal rotation of the motor. In response to a control signal, the speed of rotation of the electric motor increases whereby respective free ends of the ionizing electrodes (6, 7) move relative to the rotation axis of the rotor under the influence of centrifugal force thereby contacting the cleaning unit (19) and removing dust collected on the electrodes.

Description

Bipolar ion generator with cleaning of ionizing electrodes

Field of the Invention

The invention relates to a bipolar ion generator having means for cleaning the ionizing electrodes.

Background of the Invention

US Patent No. 5,768,087 discloses a device for bipolar ionization where cleaning dust from the ionizing electrodes is performed automatically. In this device the electrodes are stationary and the electrode cleaning device is installed on the rotating part of the ventilator. The cleaning device is operated by centrifugal force.

A drawback of this device is the large and unregulated number of cleaning cycles activated every time the generator is switched ON and OFF, which results in quick wear of the cleaning device.

US Patent No. 7,969,707 discloses a device for bipolar ionization with automatic electrode cleaning facility, in which both the ionizing electrodes and the cleaning device are mounted on the rotating part of the ventilator. The cleaning device is operated by means of centrifugal force.

A common drawback of the above devices is their unsuitability for use in ventilation and air conditioning systems in buildings and premises where the time intervals between switching the systems ON and OFF are longer than the time it takes for the electrodes to become dirty, in particular in systems operating in non-stop mode, where cleaning will be totally eliminated. US Patent No. 5,768,087 discloses a cleaning device coupled to a fan used for creating air flow across ionizing electrodes in an ionizer including a rotating shaft or hub. The cleaning device has a brush assembly for cleaning the ionizing electrodes. A first mechanism coupled to the brush assembly is responsive to the shaft or hub rotating at low speed below its operating speed for biasing the brush assembly towards the ionizing electrodes to provide a cleaning of the ionizing electrodes, and is responsive to the shaft or hub rotating at a high operating speed to bias the brush assembly away from the ionizing electrodes to prevent a cleaning of the ionizing electrodes.

In both of the above devices centrifugal (or more correctly "centripetal") force acts on the brush assembly in order to bring it into contact with the electrodes for cleaning.

US 2010/0188793 discloses a bipolar ionization device that automatically cleans dust from the ionizing electrodes using a cleaning device operated by a drive implemented as a bi-directional solenoid. A drawback of this device is its complexity since in addition to a solenoid and brushes, the cleaning device includes at least five elements for converting the linear movement of the solenoid to rotary movement of the brushes.

Summary of the Invention

An object of the present invention is to address at least some of the drawbacks of the above mentioned devices and also to prolong the operational life of the bipolar generator.

The objective is achieved by simplifying the cleaning device and reducing the number of cleaning cycles during the bipolar generator operation.

In accordance with the invention there is provided a bipolar ion generator configured for automatic cleaning of ionizing electrodes, said bipolar ion generator comprising:

a pair of deflectable ionizing electrodes coupled to a source of high voltage and configured for rotation about a rotation axis by a variable speed electric motor; and

a stationary cleaning unit mounted in spatial disposition with the ionizing electrodes and separated therefrom at normal rotation of the motor;

wherein in response to a control signal, the speed of rotation of the electric motor is configured to increase whereby respective free ends of the ionizing electrodes move relative to the rotation axis of the rotor under the influence of centrifugal force thereby contacting the cleaning unit and removing dust collected on the electrodes. Brief Description of the Drawings

in order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Figure 1 shows schematically a bipolar ion generator according to an embodiment of the present invention; and

Figure 2 is a schematic end elevation in the direction of arrow "A" in Figure 1 showing the change of the position of the end of an ionizing electrode with respect to different rotation speeds. Description of Embodiments of the Invention

Referring to the figures there is shown a bipolar ion generator 100 comprising a generally cylindrical hollow casing 1 having at least one aperture 2. Fixedly supported within the casing 1 is an electric motor 3 having a shaft 4 to which there is fixed a rotor 5 that is configured for rotating on the motor shaft 4 within the hollow casing 1 and which supports at least two ionizing electrodes 6 and 7 and at the least two different polarity voltage multipliers 8 and 9. The ionizing electrodes 6 and 7 are fastened to the rotor 5 with their free ends close to the outer edge of the rotor as shown in Figure 2. The electrodes 6 and 7 are rotated by the rotor 5 at a low speed so that under normal operation there is insufficient centrifugal force to deflect the ionizing electrodes relative to the rotation axis of the rotor 5.

A central circular plate 10 and a surrounding annular plate 11 are attached to an outer surface of the rotor 5 and face corresponding plates 12 and 13 fixed on an inner surface of the hollow casing, in opposition to the plates 10 and 11 and forming air capacitors that provide capacitive coupling between the high-voltage and the low-voltage outputs of an AC high voltage generator 14 and the voltage multipliers 8, 9. An ion sensor 15 is mounted on an inner surface of the casing 1 and provides an indication of the number of ions generated by the ion generator 100. The AC high voltage generator 14 is controlled by a main control unit 16 that also controls a motor control unit 17 that is coupled to the motor 3. The AC high voltage generator 14 and the control units are commonly coupled to terminals 18 used to connect the generator to an external power supply.

In order to simplify the cleaning device the ionizing electrodes 6, 7 are implemented as a thin wire made from a material with elastic properties, such as nickel- titanium (also known as Nitinol), that allow the wire to bend under strong centrifugal force, the extent of the bending varying according to the amplitude of the force (greater force resulting in greater bending).

A cleaning device shown generally as 19 is mounted in an inner cylindrical wall surface of the casing 1 and may be implemented by brushes located close to an outer surface of the rotor 5 but not so close as to contact the ionizing electrodes 6, 7 in their non-deflected state. To clean the ionizing electrodes 6, 7 the electric motor 3 is set to rotate at high-speed so that the generated centrifugal force causes the electrodes 6, 7 to deflect as shown in Fig. 2 thereby effecting mechanical contact with the cleaning device.

This configuration not only simplifies the generator but it also extends the operational life of the generator compared with known devices such as shown in US Patent Nos. 5,768,087 and 7,969,707 whose cleaning devices include a return spring, which remains stretched during the entire operational life such that the resulting metal fatigue shortens the operational life of the cleaning device.

In contrast thereto, in the bipolar ion generator 100 according to the invention the ionizing electrodes 6 and 7 are deflected only during cleaning, namely for only a few seconds during a single cleaning cycle.

Unlike the above devices, in the invention the brush constituting the cleaning device 19 remains stationary and the free ends of electrodes 6, 7 are deflected into contact with the brush under the action of centrifugal force in order to wipe the electrodes against the stationary brush. This avoids the complexity of a custom mechanism, typically employing flywheels and counteracting springs as required in known devices.

Another objective, i.e. reducing the number of cleaning cycles, is achieved by applying two technical solutions.

The first technical solution is to reduce the duration of the air contact between the ionizing electrodes and the dusted air flow. To do so, the cylindrical casing 1 is formed with at least one aperture 2 for ions to escape from the generator.

Reducing the air contact duration is determined as a ratio of the full body circumference to the aperture length. This facilitates a 2-4-fold reduction of the direct air contact between the tonizing electrodes 6, 7 and the air flow. Further reduction of the air contact duration with the electrodes is problematical without reducing the ion output level from the generator, since only some of the total number of generated ions will escape outside the generator during the air contact. The second technical solution derives from not activating the cleaning at each switching ON and OFF of the generator or at predetermined time intervals but rather by application of a signal provided by the microprocessor-based generator control unit that is generated in accordance with the effectiveness of the ionizing electrodes, which impacts the degree of ionization as measured by the ion sensor 15.

Operation of the bipolar generator 100 is as follows. Initially, the RPM value of electric motor 3 is preset to a low value (e.g. to 400 RPM) by the generator operation control unit 16 via the motor control unit 17. The AC generator 14 is switched off by the main control unit 16. This prevents high frequency noise at the output of the electric motor 3, caused by the operation of the AC high voltage generator 14.

Then AC high voltage 14 is switched on by the main control unit 16 and after the AC voltage is transmitted via the air capacitors and converted by the voltage multipliers 8 and 9, high voltage positive and negative polarity DC voltage appears across the ionizing electrodes 6 and 7.

During rotation of the rotor 5, the ionizing electrodes 6, 7 sequentially pass by the aperture 2 and the sensor 15. As the ionizing electrodes 6 and 7 pass by the aperture 2, ions escape outside the generator 100, while as they pass by sensor 15, the ionizing electrodes generate ion flow which is analyzed by the control unit 16. In the case of only a single aperture as shown in Figure 1 , during each 180° rotation of the rotor 5, the positive and negative electrodes 6 and 7, respectively, alternately sweep past the aperture 2, thus alternately releasing positive and negative ions during each half cycle. If two apertures are provided as shown in Figure 2, then during each 180° half cycle, both positive and negative ions are discharged through the respective apertures. In either case, the length of each aperture must be at the most half the circumference of the casing so that each aperture serves only a single electrode during each 180° half cycle and the polarity of the ions discharged through each aperture changes during each 180" half cycle.

In one embodiment, when the ion flow as measured by the ton sensor 15 becomes lower than a preset value, owing to dust collecting on the ionizing electrodes 6, 7, a "CLEANING" signal is generated by control unit 16. This signal is applied to the motor control input 17, which increases the RPM value of the electric motor 3 to a high value (e.g. 4,000 RPM) causing the electrodes 6, 7 to deflect and enable mechanical contact with the casing 1. In an alternative embodiment, the rotor 5 may be rotated at high speed at time intervals determined set by the control units 16 and 17, so as to deflect the electrodes 6 and 7 into contact with the cleaning device 19. In such an embodiment, cleaning is not a function of electrode efficiency and so the ion sensor 15 is not required. In yet another embodiment, the speed of the motor 3 may be adjusted manually for example by manual actuation of a switch that increases the voltage across of the motor and thereby increases its speed. In such an embodiment, the control signal is a preset voltage and the control unit 17 is constituted by a manually operated switch. Also here, since cleaning is not a function of electrode efficiency, the ion sensor 15 is again not required.

Figure 2 shows the deflection of the ionizing electrode 7 owing to the high speed of rotation of the rotor 5 coupled by the electric motor 3.

During cleaning, the control unit 16 switches the AC generator 14 off again. After the cleaning is completed, the bipolar generator operation cycle is repeated till the next cleaning cycle.

In a preferred embodiment reduced to practice, the following design parameters were employed:

Claims

1. Bipolar ion generator (100) configured for automatic cleaning of ionizing electrodes, said bipolar ion generator (100) comprising:

a pair of deflectable ionizing electrodes (6, 7) coupled to a source of high voltage (14) and configured for rotation about a rotation axis by a variable speed electric motor (3); and

a stationary cleaning unit (19) mounted in spatial disposition with the ionizing electrodes (6, 7) and separated therefrom at normal rotation of the motor;

wherein in response to a control signal, the speed of rotation of the electric motor is configured to increase whereby respective free ends of the ionizing electrodes (6, 7) move relative to the rotation axis of the rotor under the influence of centrifugal force thereby contacting the cleaning unit (19) and removing dust collected on the electrodes.

2. The bipolar generator according to claim 1 , further comprising:

a hollow cylindrical casing (1) supporting the motor on an end surface thereof, at least one aperture (2) in the inner surface of the casing for allowing ions to escape outside the casing,

a rotor (5) adapted for rotation within the casing and supporting the deflectable ionizing electrodes (6, 7),

an AC high voltage generator coupled to at least two voltage multipliers, and an air capacitor having opposing plates (10, 12) mounted respectively on the rotor and the inner surface of the casing for providing capacitive coupling between an output of the AC high voltage generator and the voltage multipliers.

3. The bipolar generator according to claim 2, wherein the cleaning unit (19) mounted is fixedly mounted to the casing of the bipolar generator.

4. The bipolar generator according to claim 2, wherein the cleaning device (19) is mounted on an internal cylindrical wall of the casing.

5. The bipolar generator according to any one of claims 2 to 4, wherein a length of the at least one aperture is at the most half the circumference of the casing.

6. The bipolar generator according to any one of claims 2 to 5, wherein the control unit is adapted to generate said control signal automatically at predetermined time intervals.

7. The bipolar generator according to any one of claims 2 to 5, further including an ion sensor (15) for generating a sensor signal indicative of a number of ions generated by the ion generator, the control unit being adapted to generate said control signal automatically in response to said sensor signal failing below a preset value.

8. The bipolar generator according to any one of claims 1 to 5, wherein the control unit (17) is operated manually.

9. Bipolar ion generator (100) configured for automatic cleaning of ionizing electrodes, said bipolar ion generator (100) comprising:

a pair of deflectable ionizing electrodes (6, 7) coupled to a source of high voltage (14) and configured for rotation by a variable speed electric motor (3);

a control unit (17) coupled to the electric motor (3) for varying the speed of rotation of the electric motor; and

wherein in response to a control signal, the control unit (17) is configured to increase the speed of rotation of the electric motor to a value that induces sufficient centrifugal force to deflect a free end of the ionizing electrodes (6, 7) into contact with the cleaning unit (19) thereby removing dust collected on the electrodes.

10. The bipolar generator according to claim 9, further comprising:

11. The bipolar generator according to claim 10, wherein the cleaning unit (19) mounted is fixedly mounted to the casing of the bipolar generator.

12. The bipolar generator according to claim 10 or 11 , wherein a length of the at least one aperture is at the most half the circumference of the casing.

13. The bipolar generator according to any one of claims 9 to 12, further comprising an ion sensor (15) for generating a sensor signal indicative of a number of ions generated by the ion generator (100), the control unit being adapted to generate said control signal automatically in response to said sensor signal falling below a preset value.

14. The bipolar generator according to any one of claims 9 to 12, wherein the control unit is adapted to generate said control signal automatically at predetermined time intervals.

15. The bipolar generator according to any one of claims 9 to 12, wherein the control unit (17) is operated manually.

16. The bipolar generator according to any one of claims 1 to 15, wherein the electrodes are formed from thin wire made from a material with elastic properties.

17. The bipolar generator according to claim 16, wherein the electrodes are formed from nickel-titanium.