WO2003070078A1

WO2003070078A1 - Automatic vacuum cleaner

Info

Publication number: WO2003070078A1
Application number: PCT/DK2003/000101
Authority: WO
Inventors: Ivar Moltke
Original assignee: Ivar Moltke
Priority date: 2002-02-19
Filing date: 2003-02-17
Publication date: 2003-08-28
Also published as: AU2003208304A1

Abstract

This invention relates to a vacuum cleaner comprising wheels (1), a core (2), a propulsion (3), and a cleaning nozzle (4) characterized in that said wheels are rotation symmetrical around their axis (1.4), preferably with a hemispherical shape (1.1), enclosing the vacuum cleaner. The propulsion motor and transmission between the core (2) and the wheels (1) makes the invention move forward as long as the torque from the centre of gravity below the rotation axis (1.4) is larger than the torque from the rolling resistance. The random movement is achieved as a result of the shape and is fully functional without mechanical steering or electronic control. When the automatic vacuum cleaner hits furniture or other objects on the floor it performs a completely elastic collision bouncing the automatic vacuum cleaner off to a new direction. The cleaning nozzle (4) is situated between said to wheels (1) and points toward the floor (or downward) due to the gravitation forces. The cleaning nozzle passes over the surface of floor (or other objects). A high speed air flow in the cleaning nozzle fluidises dust (and other particles as well), and airborne dust follow the air flow up through the vacuum duct toward the dust container. This invention further relates to a cleaning nozzle.

Description

Automatic vacuum cleaner

The present invention relates to a vacuum cleaner and a cleaning nozzle.

This invention is in the field of robot vacuum cleaners. In the art, it is known that robot vacuum cleaners so far have focused on vacuum cleaners of standard size fitted with sensors, positioning systems or other high tech devices for navigating the robot and an onboard computer to serve the navigation.

GB 2.369.558 discloses a self propelled bare floor cleaner, where a sphere is moving the cleaning device, said sphere being moved by a balance rotating within the sphere. Said self propelled bare floor cleaner uses a dust cloth to clean. Said dust cloth is to be sprayed with a cleaning solution in order to collect dust and debris.

However, the above prior art involves the problem that when the dust cloth of said floor cleaner is dirty, it has to be removed, cleaned and attached to said floor cleaner again before the floor cleaner can be used again to clean.

Further, the prior art involves the problem that it is difficult to see when the dust cloth has a limited cleaning effect, i.e. when it is filled with dirt or worn, etc.

Additionally, the prior art involves the problem that the self propelled bare floor cleaner is easily trapped, for instance when it's the dust cloth is caught by splinter of wooden parts, e.g. splinter in the floor or furniture, etc.

Further, the self propelled bare floor cleaner involves the problem that it is too easily trapped by obstacles since the relative large size of said dust cloth prevents the floor cleaner from moving between obstacles, e.g. close space furniture legs. In other words, the large size of the bare floor cleaner with the attached dust cloth prevents it from moving and passing behind and below furniture and other obstacles.

Other critical problems of contemporary automatic vacuum cleaners are high sales prices due to high complexity, very expensive accumulators in order to provide enough power, and a large size of the automatic vacuum cleaners, which prevent their access behind and below furniture and similar obstacles.

The prior art of vacuum cleaners involve the problems of numeral components increasing the cost and the problem of a design with a large resistance to the air flow increasing the demand for costly accumulators in automatic vacuum cleaners.

It is therefore an object of the present invention to provide a vacuum cleaner with a simple dust collection system.

It is therefore a further object to provide a vacuum cleaner that can move between and close to obstacles without being stopped by the obstacles.

It is therefore an additional object to provide a vacuum cleaner of a suitable size, at a low price and with a relatively low power consumption.

It is therefore a further object to provide a cleaning nozzle with good cleaning performance at low power consumption.

It is therefore an additional object to provide a combined cleaning nozzle, fan and motor reducing the number of components.

The above objects are achieved by said vacuum cleaner, when it comprises wheels, a core, propulsion and a cleaning nozzle. Said propulsion are rotating said rotation symmetrical wheels around their axis, preferably said wheels have a hemispherical shape and enclose said core in such a way that said cleaning nozzle is positioned in proximity to said horizontal surface and said cleaning nozzle is below the centre of gravity of said core and said core having a centre of gravity below said axis of said wheels, and that said core comprises a dust container, a motor, a fan, ducts a cleaning nozzle and a power supply.

In a preferred embodiment of the invention, said dust container is transparent. In a preferred embodiment of the invention, said ducts are connected through said cleaning nozzle for recirculation of an airflow containing a flow from a centre exhaust duct to a surrounding vacuum inlet guided by a curtain of brushes or flaps.

In a preferred embodiment of the invention, said core is separated in parts connected with a hinge, a lock, which can be released by a press and clicked to lock, and sealed by an airtight seal.

In a preferred embodiment of the invention, the vacuum cleaner further comprises a control-system using sensors preventing said vacuum cleaner from being caught by an obstacle and from being damaged.

In a preferred embodiment of the invention, said control system can power each of said wheels separately.

In still a preferred embodiment of the invention, the vacuum cleaner further comprises accessories such as a handle, a dust bag, wheel covers and/ or a docking station.

According to the invention, the cleaning nozzle of the vacuum cleaner comprises a vacuum duct surrounding an exhaust duct and a fan.

In a preferred embodiment of the invention, said cleaning nozzle is asymmetrical around its rotation axis.

In a still preferred embodiment of the invention, said cleaning nozzle is integrated in a motor and has a common rotation axis with said motor.

In a preferred embodiment of the invention, it further comprises rotating brushes.

In a still yet preferred embodiment of the invention, an outside periphery of said cleaning nozzle is a toothed rim, and said toothed rim drives at least one wheel. In a still yet preferred embodiment of the invention, a primary induction coil can be inserted in said cleaning nozzle transforming power inductively to a secondary coil representing windings of coil of said motor

It is a further advantage of the invention that the vacuum cleaner's relatively large wheels are taking it across obstacles.

It is a further advantage of the invention that it has a low price due to its simplicity and consumes little energy and consequently has less expensive batteries.

The invention will be explained more fully below in connection with preferred embodiments and with reference to the drawings, in which:

fig. 1 shows wheels;

fig. 2 ( 2.1 , 2.2, 2.3, 2.4, 2.5, 2.6, 2.7 ) shows a core; fig. 2.1 core fig. 2.2 dust container fig. 2.3 motors fig. 2.4 fans fig. 2.5 ducts fig. 2.6 power fig. 2.7 hinges, locks and seals fig. 3 shows propulsion;

fig. 4 ( 4.1 , 4.2, 4.3, 4.4, 4.5 ) shows a cleaning nozzle; fig. 4.1 vacuum duct surrounding exhaust duct fig. 4.2 vacuum duct following periphery fig. 4.3 ducts through motor fig. 4.4 nozzle with toothed rim for propulsion fig. 4.5 asymmetrical nozzle fig. 5 (5.1 , 5,2, 5.3, 5.4) shows a control system; fig. 5.1 magnetic sensor fig. 5.2 radar sensor fig. 5.3 tilt sensor fig. 5.4 direction sensor and homing path fig. 6 shows accessories;

fig. 7 shows an exploded view of the embodiment of a automatic vacuum cleaner and fig. 8 shows an embodiment of a automatic vacuum cleaner

Throughout the drawing a hierarchical notation is used, i.e. the generic numeral 1 relates to 1.1 1.2 1.3, and in some instances 1 also relates to 1.1.1, 1.1.2, 1.1.3, etc. The same applies to top level hierarchical notations 2, 3 etc.

In general the present invention is constructed from the following elements: generic reference numeral 1 (1.1, 1.2, 1.2.1.1....) as Wheels, generic reference numeral 2 (2.1 , 2.2, 2.2.1.1....) as core, generic reference numeral 3 (3.1, 3.2, 3.2.1.1....) as propulsion, generic reference numeral 4 (4.1 , 4.2, 4.2.1.1....) as cleaning nozzle, generic reference numeral 5 (5.1, 5.2, 5.2.1.1....) as control-system and generic reference numeral 6 (6.1, 6.2, 6.2.1.1....) as accessories.

Figure 1 shows wheels. The shape of the wheels can be any convex geometry rotation symmetrical shape around the axis, i.e. reference numeral 1.1 shows a hemispherical shape of the wheels, reference numeral 1.2 shows a half ellipsoid shape of the wheels or reference numeral 1.3 shows covers covering the wheels. Reference numeral 1.4 shows the rotation axis of the wheels.

The wheels can be made from stainless steel, steel, aluminium, polymer, they can be covered with Teflon, covered with decorative covers, covered with friction material along the edges, covered with brushes, covered with shock absorbing material, or coved with sound absorbing material.

The wheels should preferably be smooth to avoid scratching furniture and other obstacles, perfectly rotation symmetrical shaped to minimize friction, elastic and /or soft to avoid damage in collisions with furniture and other obstacles, have an area with high friction along the periphery of the rotation symmetrical wheels. Said decorative covers could be clipped on or added to the wheels. Said decorative covers may look like fruits, animals, the globe, or any other objects with a spherical shape, said decorative covers may be with logos or other commercial advertising, with void surface, i.e. it may be decorated by the consumer, further said decorative covers may be with any colour or pattern.

Said covers could also be made from alternative materials, such as wood, marble, ceramics, etc.

The two wheels can be mechanically connected to each other.

Any combination of these effects may be applied according to the invention.

Figure 2.1 , 2.2, 2.3, 2.4, 2.5, 2.6, 2.7 shows the core.

Figure 2.1 shows that said core comprises reference numeral 2.1 as chassis, reference numeral 2.2 as a dust container which may be a part of the chassis, reference numeral 2.3 as a motor, reference numeral 2.4 as a fan, reference numeral 2.5 as ducts, reference numeral 2.6 as power supply, and reference numeral 2.7 as locks and hinges to provide access to the inner of said core and 3.1 as propulsion motor.

Said chassis is the structure of the automatic vacuum cleaner on which all other components are mounted. In most cases the dust container and the ducts are integrated in said chassis. Said chassis can be made from polymer, metal or organic fibres

Figure 2.2 shows several versions of generic dust container reference numeral 2.2. Said dust container can be made in transparent materials to visualise when the container is full and need to be emptied.

Air and dust are separated in said dust container. This separation can be obtained by reduced airspeed - as shown by reference numeral 2.2.1 - due to the fact that said container is wider than the piping. Air and dust may also be separated in said dust container - as shown by reference numeral 2.2.2 - where a double cyclone spins the air and separates the heavier dust from the lighter air using the centrifugal effect.

Air and dust may alternatively or additionally be separated in said dust container where the dust bag reference numeral 6.5 separates the dust and the air by means of a filter.

Any combination of these effects, i.e. reference numerals 2.2.1 , 2.2.2 and 6.5 may be applied according to the invention.

Figure 2.3 shows the motor generic reference numeral 2.3 can be of various types, i.e. reference numeral 2.3.1 as a normal DC brush type with an internal rotor, reference numeral 2.3.2 brushless type, reference numeral 2.3.3 as a motor with an external rotor, reference numeral 2.3.4 a special motor with a hole in the centre, or reference numeral 2.3.5 as a special motor with a hole in the centre and bearings along the periphery.

The brushless type has a higher efficiency and higher start torque but needs a converter from DC to AC. The external rotor type has a higher start torque and better cooling.

Any of said motors 2.3.1. , 2.3.2, 2.3.3, 2.3.4, 2.3.5 may be applied according to the invention.

Figure 2.4 shows the fan generic reference numeral 2.4 can be of various types, i.e. reference numeral 2.4.1 as a centrifugal type, reference numeral 2.4.2 as a propeller type, reference numeral 2.4.3 a the centrifugal type with a Coanda effect, and reference numeral 2.4.4 as the propeller type with Coanda effect

Said fan can preferably move the air in the exhaust duct reference numeral 2.5.2 but can also more the air in the vacuum duct 2.5.1 or in both ducts.

Any of said fans 2.4.1 , 2.4.2, 2.4.3, 2.4.4 may be applied according to the invention. Said fan can be positioned in various places with respect to said motor, i.e. as shown by reference numeral 2.4.5 around the motor, as shown by reference numeral 2.4.6 connected to the motor with an axis, or as shown by reference numeral 2.4.7 positioned in the centre of the motor or as shown by reference numeral 2.4.8 with the fan rotating around a horizontal axis.

Any of said fan positions 2.4.5, 2.4.6, 2.4.7, 2.4.8 may be applied according to the invention.

Figure 2.5 shows the vacuum duct, reference numeral 2.5.1 , and the exhaust duct - shown by reference number 2.5.2 -can be integrated in the core in various ways. Any of said duct positions may be applied according to the invention

Figure 2.6 shows the power supply generic reference numeral 2.6 can be implemented in various ways. i.e. reference numeral 2.6.1 by means of standard batteries or accumulators, e.g. a NiMH, Lithium Ion, or NiCd type, reference numeral 2.6.2 by means of cell phone type of flat accumulators or as fuel cells.

Any of said power supply variants may be applied according to the invention.

The Lithium Ion accumulators charge faster, provide a higher voltage and are more expensive.

Fuel cells have a significantly higher energy density than rechargeable batteries and will thus provide a interesting capacity boost in automatic vacuum cleaners. Fuel cells can be refilled with hydrogen, methane, methanol or other fuels with hydrogen. Such a refill is faster than recharging batteries.

The power supply can be placed where there is room for it, e.g. as shown by reference numeral 2.6.2 in the core, or as shown by reference numeral 2.6.3 in the wheels. As an example, flat polymer accumulators known from cell phones are particularly suitable for placement in the wheels. Any of said positions of power supply variants may be applied according to the invention.

Figure 2.7 shows locks, hinges and seals generic reference numeral 2.7 provide access to the core. The access to the dust container reference numeral 2.2 in the core reference numeral 2.1 can be provided trough reference numeral 2.7.1, i.e. hinges, reference numeral 2.7.2 locks between two sections of the core and reference numeral 2.7.3 seals.

The core is preferably split in two, providing access to inspect, empty and clean the dust chamber, ducts, ventilation housing, fan and/or motor. This design also makes it easy to install the fan and motor in a manufacturing process.

Figure 3 shows propulsion. The propulsion is a combination of reference numeral 3.1 as a motor and reference numeral 3.2, as a transmission.

Said transmission can be implemented in various ways, i.e. the transmission can be reference numeral 3.2.1, i.e. the fan motor reference numeral 3.1~2.3.5 (as the fan motor is also the propulsion motor) with a toothed rim driving one of the wheels preferably through an toothed rim integrated in the wheels, reference numeral 3.2.2, i.e. a planetary gear integrated with the motor reference numeral 3.1, reference numeral 3.2.3 as a toothed rim integrated in the wheels, or as reference numeral 3.2.4 where wheels are transmitting propulsion from one wheel to the other, or as reference numeral 3.2.5 where said transmission wheels are connected directly to the motor reference numeral 3.1

Any of said propulsion and transmission variants may be applied according to the invention.

Figure 4 shows cleaning nozzles. The figures to the left illustrate a cross section perpendicular to the rotation axis and the figures to the right illustrates a cross section in the rotation axis. The geometry of the cleaning nozzle for re-circulation may be defined by reference numeral 1 wheels on two sides, reference numeral 4.1 curtains on the two remaining sides, reference numeral 4.2 the floor surface below kept at a well defined distance by the wheels, and reference numeral 4.3, i.e. the "ceiling" of the cleaning nozzle convex curved in order to reduce the distance between said "ceiling" and floor half way between exhaust duct and vacuum duct. This reduction in cross section increases the air speed and vacuum, and thus improves performance in vacuum cleaning.

The vacuum duct 2.5.1 must surround the exhaust duct 2.5.2 to make sure that all dust remaining in the exhaust air will return to the dust container and in order to avoid that the exhaust air push the dust away.

Figure 4.1 shows said cleaning nozzle in combination with vertical ducts ( see also figure 2.5 ).

Figure 4.2 shows said cleaning nozzle in combination with a vacuum duct reference numeral 2.5.1 following the periphery of the core

Figure 4.3 shows a cleaning nozzle with said fan reference numeral 2.4 in the centre of the motor reference numeral 2.3.5.

Figure 4.4 shows a cleaning nozzle with said fan reference numeral 2.4 in the centre of the motor reference numeral 2.3.5 and with integrated propulsion gear wheels and toothed rim reference numeral 3.2.1 and rotating brushes reference numeral 4.4.

The centre of the cleaning nozzle can be integrated with the fan rotating around a vertical axis. Brushes, reference numeral 4.4, mounted on this rotating cleaning nozzle will also rotate around a vertical axis.

The problem of rotating brushes is that they tend to catch treads from carpets and wind them up, and eventually stop rotating. The vertical rotating brushes in combination with soft brushes might be less risky as pulling the treads will loosen rather than fasten the grip. Figure 4.5 shows an asymmetrical nozzle reference numeral 4.5 with a conical nozzle, rotating at high speed. Said asymmetrical nozzle can cover the width of the rotating area. The dust will experience such a asymmetrical rotating nozzle as a fluctuating airflow pulling adhesive objects more efficiently off the floor. The asymmetrical design must be balanced to avoid vibrations.

Said cleaning nozzle may be down or up-scaled in size, i.e. it may applied in any application vacuuming particles, dirt, fluids, gas, or combinations thereof, etc.

Any of said cleaning nozzle variants may be applied according to the invention.

Figure 5 shows a functionality of the control system. The control system is a combination of:

- Generic reference numeral 5.1 as sensors, reference numeral 5.1.1 magnetic sensor, reference numeral 5.1.2 radar sensor, reference numeral 5.1.3 tilt sensor, reference numeral 5.1.4 temperature sensor sensing motor overload, e.g. too hot, and as reference numeral 5.1.5 sensors sensing sounds like a persons whistle or clap. -CPU reference numeral 5.2 -Wiring reference numeral 5.3 -Alarms (lamp, speaker, etc.) reference numeral 5.4 -Clutch reference numeral 5.5 -Magmetic strip reference numeral 5.6 -Manual on-off switch 5.7 (se figure 9)

The CPU can be of a simple wiring, e.g. gates combines with sensors and switched outputs, wiring combined with switches, e.g. gates or higher level logic building blocks (RAM, ROM) combined with sensors and switched output(s), or as a dedicated microprocessor programmed for the purpose, i.e. taking action based on sensors, etc.

Converters for brushless motors can be integrated in said CPU Figure 5.1 shows how the magnetic sensor reference numeral 5.1.6 detects a magnetic strip reference numeral 5.6

Figure 5.2 shows how a radar sensor reference numeral 5.1.2 uses any frequency of radio, light or sound to detect the absence or reduction of reflection of radio waves, infrared, light, ultrasound or any other wavelength to detect that the floor is ending or changing level downward.

Figure 5.3 shows how the tilt angle sensor reference numeral 5.1.3 can detect rotation of the core reference numeral 2. This rolling automatic vacuum cleaner is very rarely trapped, for instance when cornered between soft materials, such as cushions, etc or trapped by obstacles it could pass at high speed but not a low speed. When the automatic vacuum cleaner hits a corner or other obstacles blockading further progress, the torque from the friction is larger than the torque of gravity and the vacuum cleaner core starts rotating within the wheels, flipping the automatic vacuum cleaner backwards. When the core is tilted a significant angle with horizontal A sensor, reference numeral 5.1.3 sends a signal to switch to reverse the propulsion motor 3.1 and hereby make the automatic vacuum cleaner run in the opposite direction for a short while. Several reversals in row could turn the automatic vacuum cleaner off and turn on an alarm (e.g. light or sound), reference numeral 5.4 The reversal is however not an option if the same motor controls the fan and the propulsion as it would vacuum the dust from the dust container to the floor. In that case the clutch reference numeral 5.5 can be released to make only one wheel rotate, or the two wheels can be rotated separately.

Figure 5.4 shows how a simple homing device is based on a radio signal from the docking station and an antenna reference numeral 5.1.1 sensing the strongest signal and thus the direction of the docking station. The automatic vacuum cleaner is turning towards reference numeral 6.2 docking station guided by reference numeral 5.1.1 antennas.

Said two wheels reference numeral 1 are normally connected or synchronised in order to make the device roll forward. An on-off clutch, reference numeral 5.5, can release this connection for a controlled period, making the automatic vacuum cleaner rotate a controlled angle

The present invention of the vacuum cleaner makes it move randomly around without any advanced intelligent guidance. If however an intelligent guidance proves to more efficient, convenient or preferable, it can be integrated in the present design using two motors for propulsion or using the clutch reference numeral 5.5. When two motors are controlled independently, the present invention of the vacuum cleaner can be controlled very accurately. It can turn on the spot if one motor is moving forward and the other reverses and vice versa; it can turn when the motors run at different speeds, and it can brake and reverse if both motors reverse.

Figure 6 shows accessories. The accessories may comprise reference numeral 6.1 an induction charger, reference numeral 6.2 as a docking station, reference numeral 6.3 a voltage transformer/charger, reference numeral 6.4 as a handle, and / or reference numeral 6.5 as a dust bag.

The automatic vacuum cleaner can be recharged placed in an induction re- charger, reference numeral 6.3 with the primary coil on the charger reference numeral 6.3. land the secondary coil in the automatic vacuum cleaner reference numeral 6.1.1 receiving energy trough induction or when placed in a docking station. Said induction receiver can be the electric coils in the fan motor reference numeral 2.3.4. reducing power supply to a primary electric coil for 230 V or 110 V supply reference numeral 6.3.1 inserted into said cleaning nozzle and using the electric coil in the motor reference numeral 2.3.4 as the secondary coil in the power transformer. A special control is necessary to distinguish between said motors two operating modes as motor and charger.

The docking station, reference numeral 6.2, can include a homing device to guide the automatic vacuum cleaner back to the docking station, which is otherwise as described above

The present invention can be used as a handheld vacuum cleaner if a stick with handle, reference numeral 6.4, is attached to the vacuum cleaner. Any of said accessory variants may be applied according to the invention.

Figure 7 shows an exploded view of the embodiment of the automatic vacuum cleaner

Figure 8 shows one embodiment of the automatic vacuum cleaner.

Figure 9 shows one embodiment of the automatic vacuum cleaner.

The movements of the automatic vacuum cleaner is explained in the following.

The propulsion motor and transmission between the core and the wheels makes the invention move forward as long as the torque from the centre of gravity below the rotation axis is larger than the torque from the rolling resistance

The random movement is achieved as a result of the shape and is fully functional without mechanical steering or electronic control. When the automatic vacuum cleaner hits furniture or other objects on the floor it performs a completely elastic collision bouncing the automatic vacuum cleaner off to a new direction.

The smooth shape reduces the risk that the roller vacuum cleaner is caught by furniture.

The relatively large diameter wheels climb over obstacles and the small size makes the vacuum cleaner access point, e.g. on a floor in a room to be cleaned.

The operation of the automatic vacuum cleaner is further stabilised by the distance bejween the rotation symmetrical wheels and by the gyroscopic effect of the ventilation fan and motor When the automatic vacuum cleaner hits a corner or other obstacles blockading further progress, the torque from the friction is larger than the torque of gravity and the vacuum cleaner core starts rotating inside the wheels, flipping the automatic vacuum cleaner back-wards. Combined with small differences in the friction of the two rotation symmetrical wheels this will normally be enough to get the automatic vacuum cleaner "off the hook".

If it is still stuck, sensors will react on the repeating tilts and turns and let the electronic control switch the DC making the automatic vacuum cleaner back off.

This way the automatic vacuum cleaner moves randomly around the floor. It tends to move more along the walls and around obstacles which is exactly where the dust sediments. This way the random movement is more efficient than a guided one. The random movement also tends to attack the dust from different angles every day making it more likely during a weeks cleaning to get all the sticky particles.

The geometry occasionally tilts the rotation axis of the automatic vacuum cleaner 15-25 degrees when it moves along walls. In this condition the functionality of the cleaning nozzle is changed as the distance between exhaust duct and the floor is increased and the ground effect reduced. The result is that the exhaust air will blow a jet towards the wall or panel, blowing dust away from the walls into the floor where it is within reach of the automatic vacuum cleaner. This is an advantage as the cleaning nozzle of automatic vacuum cleaner can not get closer than 3-4 cm from the obstacles.

The small size is a trade off between capacity and functionality. Increased size provides space for more power, larger dust container and wider cleaning "track". The size is however restricted by accessibility to every corner of the room, below sofas, beds, chairs and most chests, and damage risk due to impact energy when it hits something

Burglar alarms may be triggered by automatic vacuum cleaner. Most detectors in burglar alarms are using the infrared spectrum to detect movements. As the present invention consumes approximately 50 W it is significantly warmer than its surroundings and thus easy to detect. However, if the surface is polished metal, even a ultra thin coating of for instance stainless steel or aluminium, it will not radiate this heat and are in most cases not detected by the burger alarm. The surface has to be cleaned to maintain this funtionality. The transparent surfaces of said dust container can be covered by a invisible non radiating coating.

The cleaning function the automatic vacuum cleaner is explained in the following.

This description follows the flow of air and dust.

The cleaning nozzle is situated between said to wheels and points toward the floor (or downward) due to the gravitation forces.

The cleaning nozzle passes over the surface of floor (or other objects). A high speed air flow in the cleaning nozzle fluidises dust (and other particles as well), and airborne dust follow the air flow up through the vacuum duct toward the dust container.

In the dust container the air and dust are separated.

The air passes from the dust container to the fan. This fan has to generate a high speed air flow and a sufficient vacuum to draw the air trough the cleaning nozzle, piping and dust container in spite of the resistance and pressure drop.

In order to reduce power demand the following design consideration shape the design of the vacuum cleaner:

The ducts are short and have a smooth surface, a reasonable constant cross section and no sharp bending.

The filters are preferable made obsolete, i.e. not needed, by the design of the dust container or cyclone in combination with recirculation of the air. ln ordinary vacuum cleaners the exhaust air is passing through the electrical motor in order to cool it. In the present invention the loss in air speed from passing through the motor is avoided as the low effect motor can be cooled from the airflow around the motors outside surface, or the passage trough the motor is made wide and smooth. To increased cooling said fan can be attached directly to the motor and made from aluminium or other heat conducting materials.

Ordinary propeller fans and impellers will not work efficiently with this pressure difference, while centrifugal fans are suitable.

A special "Coanda effect" design of the fan with a small distance between the "blades" and a curving of the blades reducing the distance in the direction of the forced airflow which provides that the fan that cannot stall. It is particularly efficient in a vacuum cleaner.

The air flow continues from the fan to the cleaning nozzle.

The geometry of the cleaning nozzle for re-circulation is defined by The wheels on two sides, curtains on the two remaining sides, the floor surface below kept at a well defined distance by the wheels.

The "ceiling" of the cleaning nozzle convex curved in order to reduce the distance between said "ceiling" and floor half way between exhaust duct and vacuum duct. This reduction in cross section increases the air speed and vacuum thus improving performance.

The vacuum duct must surround the exhaust duct to make sure that all dust remaining in the exhaust air will return to the dust container and in order to avoid that the exhaust air push the dust away.

An electrical motor, preferable a DC motor, makes the fan rotate at high speed. This motor can be of the ordinary internal rotor brush type, and it can be brushless thereby decreasing dimensions and increasing energy efficiency. The motor can also be of the external rotor type. The external rotor motors have a somewhat better torque, better cooling since the heat is generated close to its surface, and it has typically a larger diameter and a reduced height compared to the internal rotor type.

The invention moves at approximately 1 meter/sec for around 2000 seconds covering a 10 m² floor randomly. With a 3 cm wide cleaning nozzle this area of the floor is in average covered 6-7 times. If the floor is larger than 10-20 m² an extra unit is needed for every 10-20 m², or a docking station with homing and recharging functionality is needed.

When the user returns home, a loud whistle, clap of hands or outburst could make the automatic vacuum cleaner answer with a beep and flashing a light to make the user find it, hold it over the garbage can, empty the dust container with the pres of a fingertip, and return it to its charger. Please notice that the dust container may need to be emptied several times a week. This will prevent the growth of mites and bacteria in the dust container.

In the claims, any reference signs placed between parentheses shall not be constructed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

The invention can be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means can be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. A vacuum cleaner for cleaning of a horizontal surface, said vacuum cleaner comprising wheels (1), a core (2), a propulsion (3), and a cleaning nozzle (4) characterized in that said wheels are rotation symmetrical around their axis (1.4), preferably said wheels have a hemispherical shape (1.1) and enclose said core in such a way that said cleaning nozzle is positioned in proximity to said horizontal surface and said cleaning nozzle is below the centre of gravity of said core and said core having a centre of gravity below said axis of said wheels, and that a propulsion motor rotates said wheels relative to said core and that said core comprises a dust container (2.2), a motor (2.3), a fan (2.4), ducts (2.5), a cleaning nozzle (4) and a power supply (2.6).

2. A vacuum cleaner according to claim 1 , characterized in that said dust container is transparent.

3. A vacuum cleaner according to claims 1 or 2, characterized in that said ducts are connected through sad cleaning nozzle for recirculation of an airflow containing a flow from a centre exhaust duct (2.5.2) to a surrounding vacuum inlet (2.5.1) guided by a curtain of brushes or flaps.

4. A vacuum cleaner according to any one of claims 1 to 3, characterized in that said core is separated in parts connected with a hinge (2.7.1), a lock (2.7.2), which can be released by a press and clicked to lock, and sealed by an airtight seal (2.7.3).

5. A vacuum cleaner according to any one of claims 1 to 4 further comprising a control-system (5), characterized in that said control system uses sensors (5.1.1, 5.1.2, 5.1.3, 5.1.4, 5.1.5) preventing said vacuum cleaner from being caught by an obstacle and from being damaged.

6. A vacuum cleaner according to any one of claims 1 to 5 characterized in that said control system can power each of said wheels separately.

7. A vacuum cleaner according to any one of claims 1 to 6 further comprising accessories such as a handle, a dust bag, wheel covers and/ or a docking station.

8. A cleaning nozzle (4.5) characterized in that said cleaning nozzle comprises a vacuum duct (2.5.1) surrounding an exhaust duct (2.5.2) and a fan (2.4).

9. A cleaning nozzle according to claim 8 characterized in that said cleaning nozzle is asymmetrical around its rotation axis (4.5).

10. A cleaning nozzle according to claim 8 or 9 characterized in that said cleaning nozzle is integrated in a motor and has a common rotation axis with said motor.

11. A cleaning nozzle according to any one of claims 8 to 10 characterized in that said cleaning nozzle further comprises rotating brushes (4.4).

12. A cleaning nozzle according to any one of claims 8 to 11 characterized in that on an outside periphery of said cleaning nozzle is a toothed rim (3.2.1), and that said toothed rim drives at least one wheel (1 ) .

13. A cleaning nozzle according to any one of claims 8 to 12 characterized in that a primary induction coil (6.3.1) can be inserted into said cleaning nozzle transforming power inductively to a secondary coil representing coil of said motor.