WO2023073468A1

WO2023073468A1 - Apparatus for improved cleaning using microwave enegry

Info

Publication number: WO2023073468A1
Application number: PCT/IB2022/059770
Authority: WO
Inventors: Mathys Johannes Rossouw
Original assignee: Microwave Solutions Gmbh
Priority date: 2021-10-27
Filing date: 2022-10-12
Publication date: 2023-05-04
Also published as: CA3236705A1; AU2022374591A1

Abstract

The invention provides a cleaning apparatus (10) which includes a tub (12) which has a first circumscribing wall (14) and a pair of opposed sidewalls (16, 18) positioned on a rotational axis, an enclosure (22) defined within the first wall and the sidewalls, a drum (24) positioned inside the enclosure, and which includes a second circumscribing wall (28), a pair of opposed end walls (30, 32) positioned on the rotational axis, a cavity (34) defined within the second wall and the end walls, into which an item to be cleaned is placed, and a drive means (27) which is connected to the drum to provide rotational movement to the drum about the axis, characterized in that the cleaning apparatus includes a plurality of microwave generators (38A, 38B), each of which is adapted to direct microwaves into the cavity.

Description

APPARATUS FOR IMPROVED CLEANING USING MICROWAVE ENERGY

FIELD OF THE INVENTION

[0001] This invention relates to a cleaning apparatus which shows improved cleaning of physical stains on an item to be cleaned and which partially disinfects the item of microbes.

BACKGROUND OF THE INVENTION

[0002] Apparatus, such as washing machines or dishwashers, which make use of microwave energy to clean and/or dry cloth are known in the art. Also, apparatus which make use of microwave energy to sterilize objects are also known in the art. Most of these apparatus focus on using microwaves to heat the water used during the cleaning process, thereby using less energy than apparatus which make use of, for example, heating elements. Apparatus which has a drying function focus on heating the water within the wet or damp cloth or on the dishes/objects, speeding up the drying process.

[0003] Other areas of prior focus in this field have been on the positioning of the microwave-generating device (the magnetron) within the washing machine, as well as directing microwaves most efficiently to the object of interest such as the water to be heated or the fabric to be dried. U.S. Patents 4,356,640, 5,463,821 and 4,334,136 are examples of this.

[0004] An important piece of prior art in relation to the present invention is US Patent Application US2002/0062667, entitled “method and apparatus for washing items having cloth with microwaves”. The specification describes an apparatus that provides a stream of continuous microwave radiation onto wet cloth in order to agitate water and soap/detergent molecules within the cloth. The agitation comes about as a result of rotational motion of the molecules due to said microwave irradiation. The irradiation also causes an increase in the water temperature. This molecular agitation and temperature increase leads to enhanced cleaning of water with detergent.

[0005] A drawback of the apparatus is apparent upon use. It was experimentally found that, in order to avoid damage to the cloth, the microwave energy levels must be relatively low. Thus, in order to achieve enhanced cleaning results, the microwave irradiation would have to be applied for relatively long periods of time. Even then, the degree of cleaning is observed to be only marginally better than that achieved through ordinary cleaning means. The use of detergent would then be additionally needed in order to achieve the enhanced clean. The prior art therefore necessitates use of detergents to achieve significantly better cleaning effects.

[0006] It is a drawback of the prior art that the penetration of microwaves into wet textiles is restricted. This in turn limits the wash load that can be adequately cleaned without introducing mechanical movement.

[0007] Another problem with the prior art is the presence of only a single microwave generator which is positioned outside of the volume within which the item to be cleaned is located. This single generator must then emit microwaves into the volume. The result is sub-optimal power density distribution within the volume, especially if this volume is a drum of a conventional washing machine. The cleaning and/or sterilisation of the item is not optimised within a given cleaning period.

[0008] The invention at least partially addresses the aforementioned limitations of the prior art.

SUMMARY OF INVENTION

[0009] It is an object of the invention to provide an apparatus, such as, for example, a washing machine or dishwasher, for improved cleaning of laundry or dishes, by using pulsed, constant and/or distributed microwave energy which, when input to a drum of the washing machine, reduces the wash cycle, temperature and amount of mechanical washing action needed, thereby saving time and energy and limiting wear and tear on the item to be cleaned.

[0010] Reducing the wash cycle, temperature and amount of mechanical washing action needed, has the concomitant benefits of reducing the wear and tear on the clothing that is cleaned by the apparatus and, in so doing, also reducing microfiber pollution which is becoming an increasing environmental problem. Other benefits of this reduced wash cycle include a reduced risk of discoloration of the laundry items, a reduction in lime deposits and removing the need to sort garments beforehand.

[0011] It is an object of the invention to reduce the wash cycle, temperature and amount of mechanical washing action needed, by more uniformly exposing a wash load to the microwave energy input to the drum. This may be achieved by using a combination of minor mechanical movement within the drum and the use and positioning of a plurality of microwave generators. [0012] It is a further object of the invention to provide a cleaning apparatus such as, for example, a washing machine or a dishwasher, which provides not only improved stain or dirt removal, but also significant reduction in bacterial, fungal and/or viral load within or on the item being cleaned.

[0013] The invention provides a cleaning apparatus which includes: a tub which has a first circumscribing wall and a pair of opposed sidewalls positioned on a rotational axis, an enclosure defined within the first wall and the sidewalls; a drum positioned inside the enclosure, and which includes a second circumscribing wall, a pair of opposed end walls positioned on the rotational axis, a cavity defined within the second wall and the end walls, into which an item to be cleaned is placed; and a drive means which is connected to the drum to provide rotational movement to the drum about the axis; characterised in that the cleaning apparatus includes a plurality of microwave generators, each of which is adapted to direct microwaves into the cavity.

[0014] The drum may be tubular, either cylindrical or tubular polygonal in shape and configuration.

[0015] The tub may have an aperture through a sidewall and the drum has an opening through an end wall that is in register with the aperture, with the opening and the aperture concentric with the axis. [0016] Each microwave generator may be a magnetron or a solid-state microwave module. Preferably, each microwave generator is a solid-state microwave module.

[0017] Each microwave module may have, or be connected to, at least one output or antenna which is positioned to radiate microwave energy into the cavity.

[0018] The plurality of microwave generators may be connected or directly engaged to the first wall of the tub or the second wall of the drum, with each generator being positioned thereon to introduce microwaves in a radial direction into the cavity.

[0019] The microwave generators may be spaced in a direction of the axis, thereby to position each generator to radiate microwave energy across a respective circumferential segment of the first wall of the tub or the second wall of the drum.

[0020] Each circumferential segment may be irradiated by one generator each. In this, a first array of generators, the generators may be axially aligned or so as not be positioned adjacent another generator, radially offset or circumferentially/diametrically opposed.

[0021] Alternatively, the cleaning apparatus may include a plurality of generator arrays, wherein each array provides more than one generator to illuminate each circumferential segment. [0022] The generators in each generator array may be axially aligned, alternatively radially offset relatively to the other generators in the respective array.

[0023] Alternatively, or additionally to the generators engaged to the first and the second walls, all or some of the plurality of microwave generators may be connected or directly engaged to a side wall of the tub or an end wall of the drum, with each generator being positioned or adapted to introduce microwaves in the axial direction into the cavity.

[0024] In this alternative, the at least one antenna may be a radiating patch antenna.

[0025] Preferably, the radiating patch antenna is connected to an end wall of drum in a co-axial position relatively to a shaft of the drive means.

[0026] The drum may be made of a material transparent to microwave energy. Alternatively, and preferably, the drum is made of a suitable heat transmissible, yet microwave impermeable, material such as a suitable metal material.

[0027] The second wall of the drum may be penetrated with a plurality of fluid-flow holes.

[0028] With the microwave modules engaged with the first wall of the tub, and the second wall made of the microwave impermeable metal material, the plurality of holes through the second wall allows the microwave energy to enter the drum. [0029] Should the plurality of holes be small, designed only to provide a means for water to flow between the enclosure and the cavity, as an alternative, or in addition, the second wall or an end wall of the drum may include a plurality of microwave transparent windows.

[0030] The plurality of holes, alternatively the transparent windows, may be positioned on the second wall to rotate into a radially co-incident position with a respective generator.

[0031] The plurality of microwave generators may produce an aggregate microwave output power of 1 kW to 50kW.

[0032] Each microwave energy generator may be adapted to emit a continuous or a pulsed microwave power output.

[0033] Each microwave energy generator may be adapted to emit microwaves in a range 300MHZ to 30GHZ.

[0034] The cleaning apparatus may include a control circuit to which the plurality of microwave generators is connected to control and to coordinate the microwave power output of the plurality of microwave generators in terms of one or more of the following parameters: power output, phase, frequency and duty cycle.

[0035] The cleaning apparatus may include a power source such as, for example, a battery (or battery bank) or a capacitor (or capacitor bank) which is controlled or coordinated by the control circuit to provide for high power pulsed microwave output. [0036] The control circuit may include a programmable process controller and one or more sensors connected to the controller and adapted to measure one or more of the following: water temperature in the cavity, microwave field strength and microwave reflection coefficient sensor.

[0037] One of the sensors may be a shaft encoder which provides input to the controller as to the position of the shaft, and therefore the position of the plurality of microwave transparent windows, to determine the moment a respective microwave generator is initiated to introduce microwave energy into the drum.

[0038] The input from the shaft controller may be used by the controller to ensure that a generator only radiates microwaves when a transparent window is radially co-incident with the generator.

[0039] Additionally, the input from the shaft controller as to its relative position and whether it is rotating or not, may be used by the controller to ensure that the respective generator radiates microwaves into a void within the cavity. This will occur when the transparent window is not obstructed by the items to be cleaned such as when the shaft and the drum stops rotating.

[0040] Alternatively, the input from the shaft controller as to its relative position and whether it is rotating or not, may be used by the controller to ensure that the respective generator radiates microwaves onto the items to be cleaned which lie adjacent the transparent window.

[0041] The controller may be adapted to receive input from the shaft controller, and input as to whether the drum is not rotating or is rotating, to ensure that the respective microwave generator only radiates microwaves when no items to be cleaned lie adjacent a transparent window or only when the items to be cleaned lie adjacent a transparent window respectively.

[0042] It may be advantageous to co-ordinate the application of the microwaves, with some generators illuminating the items to be cleaned directly which lie co-incident to the window and other generators radiating into the void around the clothes.

[0043] Further additionally, the introduction of microwave power and the agitation of the load can be co-ordinated by the controller to maximise exposure of the items to be cleaned with the microwave energy.

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The invention is described with reference to the following drawings in which:

Figure 1 is a schematic isometric illustration of a first embodiment of a cleaning apparatus in accordance with the invention;

Figure 2 is a schematic isometric illustration of a second embodiment of a cleaning apparatus in accordance with the invention;

Figure 3 is a schematic isometric illustration of a third embodiment of a cleaning apparatus in accordance with the invention;

Figure 4 diagrammatically illustrates the cleaning apparatus of Figure 1 or

Figure 2 connected to a control system; Figure 5 diagrammatically illustrates the cleaning apparatus of Figure 3 connected to a control system; and

Figure 6 diagrammatically illustrates a fourth embodiment of a cleaning apparatus in accordance with the invention.

DESCRIPTION OF PREFERRED EMBODIMENT

[0045] Figure 1 shows a cleaning apparatus 10 in accordance with a first embodiment of the invention.

[0046] The cleaning apparatus 10 includes a cylindrical tub 12, which has a body defined by a cylindrical (or first) wall 14, and a first and second sidewall (respectively designated 16 and 18). An aperture 20 opens through the first sidewall 16. Between the first wall and the sidewalls, an enclosure 22 is defined.

[0047] It is within the enclosure 22, that a cylindrical drum 24 is contained, mounted on a shaft 26, which is connected to a drive means 27 which powers rotational movement of the drum about an axis.

[0048] The drum has, in this embodiment, a cylindrical (second) wall 28 and a pair of end walls (respectively designated 30 and 32) which enclose a cavity 34. An opening 36 penetrates the end wall 30 and is axially in register with the aperture 20.

[0049] A circular cylindrical wall 28 is not a limitation on the invention. As illustrated in Figure 2, in a second embodiment 10B, the second wall 28 of the drum has the configuration of a polygonal cylinder. It has been found that a polygonal cylinder with, for example, 5 or 6 sides, has a much more uniform microwave energy distribution than a circular, rectangular or square cylinder. This benefit may be because the radiation will be incident to the surface and the amount of refraction is reduced.

[0050] The second wall 28 is perforated with a plurality of holes (not shown), through which a washing fluid (water) moves between the enclosure and the cavity.

[0051] It is into the cavity 34 that items, such as clothing, are placed to be washed. The clothing is passed through the aperture 20 and the opening 36. The aperture will have a closure (not shown) to contain the clothing within cleaning apparatus such as a washing machine.

[0052] For ease of explanation, and to focus on the description on the invention, the plumbing system, bringing water to the apparatus and drawing water from the apparatus, as well as the heating system, provided to heat the washing medium, is not described herein.

[0053] The cleaning apparatus (10 and 10B) includes a plurality of solid-state microwave generators, respectively designated 38A and 38B, engaged to an outer surface 40 of the first wall 14. The first and second microwave generators are positioned over a first and a second circumferential segment (42A, 42B) respectively of the drum 24 (see dotted outline in Figures 1 and 2 which illustrate a notional boundary between the segments). In this example, the one generator is radially spaced or offset relatively to the other. [0054] This radial spacing is preferred to ensure that the microwave energy output of one generator does not adversely affect the functionality of another generator in an adjacent segment.

[0055] From each generator 38, one or more microwave antennae are deposed within the enclosure 22, positioned to emit microwaves into the enclosure 22. Alternatively, the first wall is penetrated with a plurality of microwave feed ports 43 (see Figure 4 and 6).

[0056] To allow microwave energy, emitted from the generators, to penetrate the second wall 28 of the drum, this wall can be made entirely of a microwave transparent dielectric such as, for example, a plastic or a ceramic material. Alternatively, this wall can be made of a suitable metal material, penetrated by a plurality of microwave transparent windows (respectively designated 44A, 44B...44N). This alternative is illustrated in Figures 1 , 2, 4 and 6. The alternative is preferred as the spin-rate of a substantially metal drum will be higher than a plastic counterpart.

[0057] Each generator can be adapted to transmit microwave energy in a range 300 MHZ to 30 GHZ. Preferably, however, the transmitted frequency is one of the frequencies allocated for industrial microwave heating (called ISM frequencies), particularly 915MHz, 2.45GHz or 5.8GHz, as these frequencies have a much lower burden of limiting detectable microwave emissions from the unit, compared to frequencies that have been allocated for other purposes, e.g., communications systems. However, choosing an ISM frequency is not a limitation on the invention as certain non-ISM frequencies may be beneficial in terms of microwave penetration, efficiency of the microwave source, or interaction with and targeting the release of certain stain types. If a non-ISM frequency is used, better screening will be needed to conform to microwave emissions regulations.

[0058] Figure 4 illustrates the cleaning apparatus (10, 10B) connected to a control circuit 50 which system includes a process controller 52 and at least one sensor 54, which in this embodiment is a shaft encoder.

[0059] The process controller is in electronic communication, via a conductor 56, to each of the microwave generators 38 and to the shaft encoder.

[0060] The shaft encoder outputs information to the controller on the relative position of the shaft 26 and, by implication, the windows 44. The controller is thus enabled to actuate each generator to emit microwaves in a synchronised manner, as a respective window passes below a respective generator.

[0061] The shaft encoder can be used to determine the most advantageous time to introduce microwave power, for instance when the windows 44 are not obstructed by the items to be cleaned. The absolute position of the drum, as well as whether its rotating at that moment, or stationary, will help in that process decision.

[0062] It may be advantageous to synchronise the application of the microwaves with the instant when the drum stops to reverse direction, or to stop rotation for that purpose. It may also be advantageous if some generators are initiated to illuminate textiles directly in front of the window and others to radiate into the void around the clothes. [0063] Additionally, the introduction of microwave power and the agitation of the load can be linked, to ensure all the items to be cleaned are exposed to the microwave energy.

[0064] Moreover, the controller can be enabled to cause each microwave generator 38 to emit a stream of microwave energy, of varying frequency. This may be done in a continually variable manner, sweeping through a predefined frequency range. Variably adjusting the frequency at which a generator emits microwaves, and controlling this adjustment relatively to the other generators, has the benefit of improving the uniformity of the microwave field i.e., the locations of the microwave hot spots (standing waves) in the cavity 34 that move around as a function of microwave frequency or wavelength.

[0065] Figure 3 illustrates a third embodiment (10C) of the invention. In describing this embodiment, like features bear like designations.

[0066] This embodiment differs from the embodiments 10 and 10B in that the plurality of microwave generators 38 are engaged to the second wall 28 of the drum 24, adapted to emit microwaves directly into the cavity 34 to aid in cleaning the items contained therein.

[0067] As illustrated in Figure 5, the cleaning apparatus 10C is connected to a control and power circuit 50 with a power line 58 and an electronic signal line 60 engaging each microwave generator to a process controller 52 via slip rings 62 on the shaft 26. [0068] The shaft encoder 54, in this embodiment, will provide a means of ensuring that only the respective generator(s) whose antennas are above the water line, or are not covered by the wash load, to switch on. In this manner, the microwaves are able to fully disperse into the cavity, reaching more of the wash load. This embodiment also has benefits in energy efficiency, as the microwave generators can be cooled by the washing water between the tub and drum.

[0069] Figure 6 illustrates a fourth embodiment designated 10D. The substantive difference between this embodiment and the earlier described embodiments is that the microwave generators 38 are not engaged to the first or second wall (14, 28) to radially emit microwave radiation but rather the generators are engaged (see generator designated 38A in Figure 6) or connected to (see generator designated 38B in Figure 6) sidewall 18 of the tub 12 to provide for axial emission of microwave energy. The advantage here is that, when the drum is rotating at high angular velocity, the wash load is flung against the inner wall of the drum by centrifugal force, covering all radial feed ports, but voiding the centre of the drum to allow unobstructed propagation of microwaves from the axial source.

[0070] The generators that are engaged directly to the sidewall, will directly emit microwaves through a respective port 43 in the sidewall and through a transparent window (44A in this illustrated example) into the cavity 34. Again, like with the earlier embodiments, this emission can be controlled/co- ordinated via a control system (not shown in this illustrated example). [0071] The generators need not be directly engaged, but merely connected as shown with respect to generator 38B. Here, the generator is connected via a co-axial cable 64 to a path antenna 66. The co-axial cable will run through the shaft 26, the shaft having a rotary joint 68 which will allow the rotation of the shaft whilst preventing the cable from twisting.

[0072] The patch antenna is lifted off the base surface (the inner surface of end wall 32) by a square or rectangular plate mounted on a di-electric backing (not shown), allowing the antenna to radiate microwaves into the cavity of the drum.

Claims

1. A cleaning apparatus which includes a tub which has a first circumscribing wall and a pair of opposed sidewalls positioned on a rotational axis, an enclosure defined within the first wall and the sidewalls, a drum positioned inside the enclosure and which includes a second circumscribing wall, a pair of opposed end walls on the rotational axis, a cavity defined within the second wall and the end walls, into v/hich an item to be cleaned is placed, a drive means which is connected to the drum to provide rotational movement to the drum about the axis, characterised in that the cleaning apparatus includes a plurality of microwave generators, each of which is adapted to direct microwaves into the cavity.

2. A cleaning apparatus according to claim 1 wherein the drum is a cylindrical or a tubular polygonal drum.

3. A cleaning apparatus according to claim 1 or 2 wherein the tub has an aperture through a sidewall and the drum has an opening through an end wall that is in register with the aperture.

4. A cleaning apparatus according to anyone of claims 1 to 3 wherein each microwave generator is a magnetron or a solid-state microwave module.

5. A cleaning apparatus according to anyone of claims 1 to 4 wherein the plurality of microwave generators is connected or engaged to the first wall of the tub or the second wall of tne drum, with each generator being positioned thereon to introduce microwaves in a radial direction into the cavity.

6. A cleaning apparatus according to anyone of claim 1 to 5 wherein the plurality of microwave generators constitutes a first array in which the generators are spaced in a direction of the rotational axis to position each generator to radiate microwave energy across a respective circumferential segment of the first wall of the tub or the second wall of the drum.

7. A cleaning apparatus according to claim 6 wherein each circumferential segment is irradiated by one generator each.

8. A cleaning apparatus according to claim 7 wherein the generators are axially aligned, radially offset or circumferentially opposed.

9. A cleaning apparatus according to anyone of claims 1 to 5 wherein the plurality of microwave generators constitutes a plurality of generator arrays in which each array provides more than one generator positioned to radiate microwave energy across a respective circumferential segment.

10. A cleaning apparatus according to claim 9 wherein the generators in each generator array are axially aligned or radially offset relatively to the other generators in the respective array.

11. A cleaning apparatus according to anyone of claims 1 to 10 wherein at least one of the microwave generators is connected or engaged to a side wall of the tub or an end wall of the drum to introduce microwaves in the axial direction into the cavity. 19

12. A cleaning apparatus according to claim 11 wherein each microwave module has, or is connected to, at least one output or antenna which is positioned to radiate microwave energy into the cavity.

13. A cleaning apparatus according to claim 12 wherein the at least one microwave generator is connected or engaged to a side wall of the tub or an end wall of the drum has a radiating patch antenna.

14. A cleaning apparatus according to claim 13 wherein the radiating patch antenna is connected to an end wall of drum in a co-axial position relatively to a shaft of the drive means.

15. A cleaning apparatus according to anyone of claims 1 to 14 wherein the drum is made of a material transparent to microwave energy.

16. A cleaning apparatus according to anyone of claims 1 to 14 wherein the drum is made of a microwave impermeable material.

17. A cleaning apparatus according to claim 16 wherein the drum includes a plurality of microwave transparent windows through the second wall or an end wall.

18. A cleaning apparatus according to claim 17 wherein the transparent windows are positioned on the second wall to be enabled to rotate into a radially co-incident position with a respective generator.

19. A cleaning apparatus according to anyone of claims 1 to 18 wherein the plurality of microwave generators produces an aggregate microwave output power of 1 kW to 50kW. 20

20. A cleaning apparatus according to anyone of claims 1 to 19 wherein each microwave energy generator is adapted to emit a continuous or a pulsed microwave power output.

21. A cleaning apparatus according to anyone of claims 1 to 20 wherein each microwave energy generator is adapted to emit microwaves in a range 300MHZ to 30GHZ.

22. A cleaning apparatus according to anyone of claims 1 to 21 which includes a control circuit to which the plurality of microwave generators is connected to control the microwave power output of the plurality of microwave generators in terms of one or more of the following parameters: power output, phase, frequency and duty cycle.

23. A cleaning apparatus according to claim 22 wherein the control circuit includes a programmable process controller and one or more sensors connected to the controller and adapted to measure one or more of the following: relative rotational position of the drum, water temperature in the cavity, microwave field strength and microwave reflection coefficient sensor.

24. A cleaning apparatus according to claim 23 wherein at least one of the sensors is a shaft encoder which provides input to the controller as to the position of the plurality of microwave transparent windows.

25. A cleaning apparatus according to claim 24 wherein the controller is adapted to receive input from the shaft controller to ensure that a generator only radiates microwaves when a transparent window is radially co-incident with the generator. 21

26. A cleaning apparatus according to claim 25 wherein the controller is adapted to receive input from the shaft controller, and input as to whether the drum is not rotating or is rotating, to ensure that the respective microwave generator only radiates microwaves when no items to be cleaned lie adjacent a transparent window or only when the items to be cleaned lie adjacent a transparent window respectively or when items to be cleaned.