WO2014194913A1

WO2014194913A1 - Cleaning device using cavitation

Info

Publication number: WO2014194913A1
Application number: PCT/DK2014/050137
Authority: WO
Inventors: Knud Erik Westergaard
Original assignee: Knud Erik Westergaard
Priority date: 2013-06-04
Filing date: 2014-05-19
Publication date: 2014-12-11
Also published as: DK177736B1

Abstract

A cleaning device (1) is disclosed, comprising a water duct having an inlet end and an outlet end, a cavity-producing element (8, 9) arranged at least partly within the water duct to perform a rotational and/or reciprocating high-speed motion for creation of cavities in water flowing through the water duct from its inlet end to its outlet end, and a nozzle (4) arranged for discharging the water from the cleaning device including the cavities formed therein by the cavity-producing element. Furthermore, a method is disclosed for cleaning and/or disinfecting a surface, said method comprising the steps of producing cavities within a flow of water by performing a rotational and/or reciprocating high-speed motion of a cavity-producing element (8, 9) within a water duct through which the water flows, and discharging the water including the cavities formed therein from the water duct onto the surface to be cleaned.

Description

CLEANING DEVICE USING CAVITATION

The present invention relates to a cleaning device, the function of which relates to the use of cavitation in water.

Background of the invention

Cavitation is the formation and then immediate implosion of cavities in a liquid, these cavities being small liquid-free zones ("bubbles"). Cavitation is the

consequence of forces acting upon the liquid. It usually occurs when a liquid is subjected to rapid changes of pressure that cause the formation of cavities where the pressure is relatively low.

Inertial cavitation is the process, in which the rapid collapse of a bubble in a liquid produces a shock wave, whereas non-inertial cavitation is a process, in which a bubble in a fluid is forced to oscillate in size or shape due to some form of energy input, such as an acoustic field.

The use of non-inertial cavitation in water for cleaning purposes is known within the art, for instance in the form of ultrasonic cleaners, in which the oscillations of the cavities are controlled by means of an ultrasonic energy field. This form of cavitation is often used for the cleaning of delicate materials, such as silicon wafers. The production of such ultrasonic cleaners is relatively costly. Other cleaning devices, such as some high-pressure cleaners, use inertial cavitation for cleaning purposes. In such devices, water under high pressure and at high speed is directed along or through suitably formed physical structures, behind which the necessary low pressure to form cavities in the water is created due to turbulence in the flow. The production and use of high-pressure cleaners, however, is known to entail a number of disadvantages such as, for instance, relatively high production costs, the need of access to a power socket for the supply of electricity to the device through a power cord and the necessary safety considerations related to the combination of water and high-voltage electricity within the device. Furthermore, it is often necessary to add chemicals to the water in order to obtain the desired effect of the cleaning, and the user is not only subject to a recoil impact from the device but also to inhalation of a mist containing not only water but also dirt and, if used, chemicals. Brief description of the invention

It is an object of the present invention to provide a cleaning device using cavitation without the above-mentioned disadvantages of devices already known in the art. The present invention relates to a cleaning device comprising a water duct having an inlet end and an outlet end, a cavity-producing element arranged at least partly within the water duct to perform a rotational and/or reciprocating high-speed motion for creation of cavities in water flowing through the water duct from its inlet end to its outlet end, and a nozzle arranged for discharging the water from the cleaning device including the cavities formed therein by the cavity-producing element.

The invention has surprisingly shown to be able to perform cleaning of at least the same efficiency as other cleaning devices known in the art, which use cavitation, although it is a much simpler construction than such known devices and, therefore, can be produced at significantly lower costs.

In an embodiment of the invention, the motion of the cavity-producing element is driven by a battery-driven electric motor. In an embodiment of the invention, the electric motor is air-cooled or water-cooled. In an embodiment of the invention, the electric motor is driven by a replaceable and/or rechargeable battery.

The use of a battery-driven electric motor means that the power cord, which is necessary for other cleaning devices known in the art, which use cavitation, can be avoided. Thus, the use of the present invention does not depend on access to high- voltage power and the device can be used anywhere.

In an embodiment of the invention, the cleaning device is arranged to be charged using a charging station.

In this way, the battery of the cleaning device can be charged in a way similar to the one used for rechargeable screwdrivers and the like.

In an embodiment of the invention, the cleaning device further comprises a regulator for controlling the speed of the motion of the cavity-producing element.

The opportunity to regulate the speed of the motion of the cavity-producing element means that the cleaning efficiency of the cleaning device can be controlled, so that the cleaning device can be used for cleaning robust surfaces as well as surfaces that are more vulnerable.

In an embodiment of the invention, the cavity-producing element is arranged to be rotated at rotational speeds of more than 5,000 rpm, preferably more than 10,000 rpm, most preferred more than 20,000 rpm.

Rotational speeds within these ranges have proven to result in cleaning efficiencies of the cleaning device suitable for cleaning robust surfaces as well as surfaces that are more vulnerable. In an embodiment of the invention, the cavity-producing element is a rotor comprising a longitudinal rotor shaft with one or more rotor vanes extending in substantially radial directions from the rotor shaft. In an embodiment of the invention, the angle between any two neighbouring directions, into which one or more rotor vanes extend from the rotor shaft, is substantially the same.

The use of a rotor shaft from which rotor vanes extend in substantially radial directions a cavity-producing element has proven to result in a stable and reliable function of the cleaning device.

In an embodiment of the invention, the cross-section of each of the rotor vanes is square, triangular or sinusoidal.

In an embodiment of the invention, the rotor vanes are substantially equally distributed along the full length of the rotor shaft.

In another embodiment of the invention, the rotor vanes are confined to a part of the rotor shaft, preferably the part nearest the nozzle of the cleaning device.

In an embodiment of the invention, the rotor vanes are made of a metal, such as brass or aluminium, of a ceramic material, such as porcelain, of a plastic material or of synthetic rubber.

In an embodiment of the invention, the cavity-producing element is exchangeable.

Using an exchangeable cavity -producing element means that different types of cavity-producing elements can be used for different cleaning and disinfecting purposes, and that worn out cavity -producing elements can be replaced. In an embodiment of the invention, a number of inward-pointing protrusion are arranged on at least a part of the inside of the water duct to reduce the rotational effect on the water caused by the rotation of the cavity -producing element. Such arrangement has a stabilizing effect of the water jet leaving the cleaning device.

In an embodiment of the invention, the cavity-producing element is held in position by one or more water-lubricated bearings. The use of water-lubricated bearings substantially reduces the wear on the cavity- producing element during operation of the cleaning device.

In an embodiment of the invention, the one or more water-lubricated bearings are mounted with a number of spokes connecting the bearings to a mounting ring fitting the inside of the water duct.

In this way, the water can pass between the bearings and the mounting rings without meeting any significant resistance. In an embodiment of the invention, the spokes are tapered in the direction facing upstream the water flow.

In this way, the resistance met by the water is reduced even further. In an embodiment of the invention, the one or more bearings are provided with a number of inward pointing protrusions and/or the parts of the cavity-producing element, which is to be placed inside the bearings, are provided with a number of countersunk grooves, which protrusions and/or grooves are arranged to cause the formation of a water film between the cavity-producing element and the bearings. This significantly reduces the friction between the cavity-producing element and the bearing and the wear of the cavity-producing element and the bearings during use of the cleaning device. In an embodiment of the invention, the cavity-producing element is arranged to be able to operate with water flowing into the inlet end of the water duct at a water pressure of less than 10 bar, preferably less than 5 bar.

The cleaning device being able to operate at water pressures so low means that the water supply to the cleaning device can simply consist in a hose connected to an ordinary tap and that the recoil impact and the mist containing dirty water and, if chemicals are used, chemical rests known from the use of high-pressure cleaners is avoided. In an embodiment of the invention, the cleaning device further comprises a water filter.

The use of a water filter for removing dirt and other impurities from the water before it enters the cleaning device is advantageous in that it can improve the function and reduce the wear of the cleaning device.

In an aspect of the invention, it relates to a method for cleaning a surface, said method comprising the steps of producing cavities within a flow of water by performing a rotational and/or reciprocating high-speed motion of a cavity-producing element within a water duct through which the water flows, and discharging the water including the cavities formed therein from the water duct onto the surface to be cleaned.

In an embodiment of the invention, the pressure of the water entering the water duct is less than 10 bar, preferably less than 5 bar. The figures

In the following, a few exemplary embodiments of the invention is described in further detail with reference to the figures, of which

Fig. 1 is a schematic cross-sectional view of a cleaning device according to an embodiment of the invention,

Figs. 2a-2c are schematic cross-sectional views of rotors of cleaning devices

according to three different embodiments of the invention, respectively,

Figs. 3-8 are schematic cross-sectional views of the outlet part of cleaning devices according to six different embodiments of the invention, respectively, Fig. 9 is a schematic side view of a bearing of a cleaning device according to an embodiment of the invention, and

Fig. 10 is a schematic side view of a part of a rotor shaft of a cleaning device according to an embodiment of the invention.

Detailed description of the invention

Fig. 1 shows a schematic cross-sectional view of a cleaning device 1 according to an embodiment of the invention.

Basically, the shown embodiment can be divided into a handle part 2, a barrel part 3 and a nozzle 4. The handle part 2 is connected to a first end of the barrel part 3 and the nozzle 4 is placed at the other end of the barrel part 3. A water duct extends throughout the cleaning device 1 from its inlet end at the bottom of the handle part 2 through the handle part 2 and the barrel part 3 to its outlet end at the nozzle 4. The figure illustrates how the water supply to the cleaning device 1 can simply consist in a water hose 5 connected to an ordinary tap (not shown). This is due to the fact that the cleaning device 1 is able to operate at very low water pressures like the ones provided in customary domestic water supplies. In the illustrated embodiment of the invention, a water filter 6 is arranged at the inlet end of the water duct between the water hose 5 and the handle part 2 of the cleaning device.

A water valve 7 is arranged within the water duct for stopping the flow of water through the water duct, when the cleaning device 1 is not operating. In the illustrated embodiment, the water valve 7 is placed in the part of the water duct passing through the handle part 2 of the cleaning device 1 but, in other embodiments, the water valve 7 can be placed anywhere in the water duct.

In the illustrated embodiment, a cavity-producing element in the form of a rotor 8, 9 extends throughout the barrel part 3 from an electric motor 10 arranged within the handle part 2 of the cleaning device 1 to the nozzle 4 thereof. In some embodiments of the invention, the electric motor 10 is air-cooled, whereas, in other embodiments, it is water-cooled. The illustrated rotor consists of a rotor shaft 8 with one or more rotor vanes 9 extending in substantially radial directions therefrom. The dimensions of the rotor shaft 8 and the rotor vanes 9 depend on the desired capacity of the cleaning device 1. Typically, the diameter of the rotor shaft 8 is a few millimetres, such as about 5 mm. In the illustrated embodiment, the rotor is held in place by three bearings, namely a rear rotor bearing 11 placed at the end of the rotor, which is connected to the electric motor 10, an intermediate rotor bearing 12 placed approximately halfway through the barrel part 3 of the cleaning device 1, and a front rotor bearing 13 placed near the nozzle 4. A gasket 14 is arranged behind the rear rotor bearing 11 to protect the electric motor 10 from water and moisture. The illustrated embodiment of the invention is provided with a device activation handle 15, which is operated similar to a trigger of a firearm. When the device activation handle 15 is pressed backwards, the water valve 7 is opened and an electric switch 16 switches on the electric motor 10 for operation of the cleaning device 1. When on the other hand, the device activation handle 15 is released again for stopping the operation of the cleaning device 1, the water valve 7 is closed and the electric switch 16 switches off the electric motor 10.

An electric battery 17 (preferably in the form of a replaceable and/or rechargeable battery, such as a lithium battery) for driving the electric motor 10, and a regulator 18 for regulating the rotational speed of the rotor 8, 9 are schematically illustrated under the barrel part 3 of the cleaning device 1 in Fig. 1. In other embodiments, however, the battery 17 and/or the regulator 18 can be placed at other positions within the cleaning device 1. In some embodiments of the invention, the cleaning device 1 can be provided with a charging station (not shown) for the battery 17 similar to the ones provided for rechargeable electric screwdrivers and the like.

During operation of the cleaning device 1, the water valve 7 is open and water flows from the water hose 5 through the water duct to the nozzle 4. The electric motor 10 is running, causing the rotor to rotate at very high speed, typically at several thousand rounds per minute. In other embodiments of the invention, this rotational motion of a cavity-producing element 8, 9 can be replaced by or combined with vibrational and/or reciprocation motions. Under-pressure behind the fast-moving vanes 9 of the rotor causes cavities

("bubbles") to be formed in the water as it flows along the rotating rotor. These cavities leave the cleaning device 1 with the water through the nozzle 4. When the water with the cavities meets a surface, shock forces related to the sudden implosion of the cavities loosen dirt from the surface and kill bacteria on the surface, whereby not only a cleaning effect but also a disinfectant effect of the invention is achieved without the use of any chemicals. In fact, this disinfectant effect has shown to be surprisingly high, meaning that a very efficient disinfection of a surface can be obtained by using a cleaning device 1 according to the present invention.

The dimensions of the cleaning device 1 vary depending on the desired cleaning efficiency, but typical embodiments are similar in size to the handheld part of common high-pressure cleaners for private or professional use.

Figs. 2a-2c are schematic cross-sectional views of rotors of cleaning devices 1 according to three different embodiments of the invention, respectively.

As illustrated in these figures, the rotor vanes 9 may extend in a number of different radial directions from the rotor shaft 8. In the illustrated embodiments, the rotor vanes 9 extend in four, two and three different directions, respectively. In other embodiments, however, the rotor vanes 9 can extend in more than four different radial directions, or they can extend in directions that are not radial in relation to the rotor shaft.

For the sake of balance of the rotor 8, 9 during operation of the cleaning device 1, it is advantageous, if the angle between any two neighbouring directions, into which one or more rotor vanes 9 extend from the rotor shaft, is substantially the same. For instance, the angle between any two neighbouring directions is 90° in Fig. 2a, 180° in Fig. 2b and 120° in Fig. 2c.

Furthermore, also for the sake of balance, it is advantageous if at least approximately the same number of rotor vanes 9 extend in each of the directions, such as every second or every fourth vane 9 extending in a given direction in Fig. 2a, every second vane 9 extending in a given direction in Fig. 2b and every third vane 9 extending in a given direction in Fig. 2c. Figs. 3-7 are schematic cross-sectional views of the outlet part of cleaning devices 1 according to five different embodiments of the invention, respectively. Figs. 3-6 illustrate how the shape of the rotor vanes 9 can vary from one embodiment to the other, the cross-section of the vanes 9 being wide square in Fig. 3, narrow square in Fig. 4, triangular in Fig. 5 and sinusoidal in Fig. 6.

Fig. 7 illustrates schematically that, whereas the rotor vanes 9 are substantially equally distributed along the full length of the rotor shaft 8 in some embodiments of the invention as illustrated in Figs. 1 and 3-6, they may be confined to a part of the rotor shaft 8, preferably the part nearest the nozzle 4, in other embodiments as illustrated in Fig. 7. It is to be understood that the different distributions of the rotor vanes 9 along the rotor shaft 8 can be combined with any of the shapes of vanes 9 illustrated in Figs. 3-6 or with other shapes not illustrated.

The rotor vanes 9 can be made from a variety of suitable materials, such as for instance aluminium or synthetic rubber. In preferred embodiments, the rotor 8, 9 is exchangeable so that different rotors 8, 9 can be used for different cleaning purposes and worn out rotors 8, 9 can be exchanged.

Fig. 8 illustrates schematically how, in some embodiments of the cleaning device 1, a number of inward-pointing protrusions 23 can be arranged in at least a part of the barrel part 3 thereof. Properly arranged, such protrusions 23 can have a stabilizing effect on the water jet leaving the cleaning device 1 by reducing the rotational effect on the water caused by the rotation of the rotor 8, 9. Fig. 9 is a schematic side view of a bearing 11, 12, 13 of a cleaning device 1 according to an embodiment of the invention.

In order to allow the flow of water through the water duct to pass by the bearing 11, 12, 13, it is advantageously mounted with a number of spokes 19 connecting the bearing 11, 12, 13 to a mounting ring 20 fitting the inside of the barrel part 3 of the cleaning device 1. In this way, the water can pass between the bearing 11, 12, 13 and the mounting ring 20 without meeting any significant resistance. This resistance may be reduced even further by tapering the spokes 19 in the direction facing upstream the water flow (not shown). An advantageous water-lubrication of the bearings 11, 12, 13 can be obtained, for instance, by providing the bearing 11, 12, 13 with some inward pointing protrusions 21 as indicated schematically in Fig. 9 and/or with providing the part of the rotor shaft 8, which is to be placed inside the bearing 11, 12, 13, with a number of countersunk grooves 22 as indicated schematically in Fig. 10. Correctly applied, such features causes the formation of a water film between the rotor shaft 8 and the bearing 11, 12, 13, significantly reducing the friction there between and the wear on the rotor shaft 8 and the bearings 11, 12, 13 during use of the cleaning device 1. This principle for obtaining water-lubrication is known, for instance, from the field of propeller shafts from the maritime industry.

List of reference numbers

1. Cleaning device

2. Handle part of cleaning device

3. Barrel part of cleaning device

4. Nozzle

5. Water hose

6. Water filter

7. Water valve

8. Rotor shaft

9. Rotor vane

10. Electric motor

11. Rear rotor bearing

12. Intermediate rotor bearing

13. Front rotor bearing

14. Gasket

15. Device activation handle

16. Electric switch for motor

17. Battery

18. Regulator for rotational speed of rotor

19. Spoke of bearing

20. Mounting ring for bearing

21. Inward-pointing protrusion in bearing

22. Countersunk groove in rotor shaft

23. Inward-pointing protrusions in barrel part

Claims

1. A cleaning device (1) comprising a water duct having an inlet end and an outlet end, a cavity-producing element (8, 9) arranged at least partly within the water duct to perform a rotational and/or reciprocating high-speed motion for creation of cavities in water flowing through the water duct from its inlet end to its outlet end, and a nozzle (4) arranged for discharging the water from the cleaning device including the cavities formed therein by the cavity-producing element. 2. The cleaning device according to claim 1, wherein the motion of the cavity- producing element is driven by a battery-driven electric motor (10).

3. The cleaning device according to claim 2, wherein the electric motor is air- cooled or water-cooled.

4. The cleaning device according to claim 2 or 3, wherein the electric motor is driven by a replaceable and/or rechargeable battery (17).

5. The cleaning device according to any of claims 2-4 being arranged to be

charged using a charging station.

6. The cleaning device according to any of the preceding claims, further

comprising a regulator (18) for controlling the speed of the motion of the cavity-producing element. The cleaning device according to any of the preceding claims, wherein the cavity-producing element is arranged to be rotated at rotational speeds of more than 5,000 rpm, preferably more than 10,000 rpm, most preferred more than 20,000 rpm.

The cleaning device according to any of the preceding claims, wherein the cavity-producing element is a rotor comprising a longitudinal rotor shaft (8) with one or more rotor vanes (9) extending in substantially radial directions from the rotor shaft.

The cleaning device according to claim 8, wherein the angle between any two neighbouring directions, into which one or more rotor vanes extend from the rotor shaft, is substantially the same. 10. The cleaning device according to claim 8 or 9, wherein the cross-section of each of the rotor vanes is square, triangular or sinusoidal.

11. The cleaning device according to any of claims 8-10, wherein the rotor vanes are substantially equally distributed along the full length of the rotor shaft.

12. The cleaning device according to any of claims 8-10, wherein the rotor vanes are confined to a part of the rotor shaft, preferably the part nearest the nozzle of the cleaning device.

The cleaning device according to any of claims 8-12, wherein the rotor vanes are made of a metal, such as brass or aluminium, of a ceramic material, such as porcelain, of a plastic material or of synthetic rubber.

14. The cleaning device according to any of the preceding claims, wherein the cavity-producing element is exchangeable.

15. The cleaning device according to any of the preceding claims, wherein a number of inward-pointing protrusion (23) are arranged on at least a part of the inside of the water duct to reduce the rotational effect on the water caused by the rotation of the cavity-producing element.

16. The cleaning device according to any of the preceding claims, wherein the cavity-producing element is held in position by one or more water-lubricated bearings (11, 12, 13).

The cleaning device according to claim 16, wherein the one or more water- lubricated bearings are mounted with a number of spokes (19) connecting the bearings to a mounting ring (20) fitting the inside of the water duct.

The cleaning device according to claim 17, wherein the spokes are tapered in the direction facing upstream the water flow.

The cleaning device according to claim 17 or 18, wherein the one or more bearings are provided with a number of inward pointing protrusions (21) and/or the parts of the cavity-producing element, which is to be placed inside the bearings, are provided with a number of countersunk grooves (22), which protrusions and/or grooves are arranged to cause the formation of a water vilm between the cavity-producing element and the bearings.

The cleaning device according to any of the preceding claims, arranged to be able to operate with water flowing into the inlet end of the water duct at a water pressure of less than 10 bar, preferably less than 5 bar.

The cleaning device according to any of the preceding claims, further comprising a water filter (6).

22. A method for cleaning and/or disinfecting a surface, said method comprising the steps of: producing cavities within a flow of water by performing a rotational and/or reciprocating high-speed motion of a cavity-producing element (8, 9) within a water duct through which the water flows, and discharging the water including the cavities formed therein from the water duct onto the surface to be cleaned.

The method according to claim 22, wherein the pressure of the water entering the water duct is less than 10 bar, preferably less than 5 bar.