Description of the prior art It is well known that these apparatuses can be equipped with a vacuum system for the removal of dust and small residues or with means for washing and/or polishing floors. In any case, these apparatuses must be controlled by an operator who provides to their locomotion and orientation.

Fully autonomously operated floor cleaning apparatuses are also known. WO00/04430, US 5781960, US 5940927 and US 5568589 disclose apparatuses of this type.

Substantially these apparatuses comprise a cleaning device, an electric supply and motor means driving a pair of wheels for their motion. Navigation sensing means allow the apparatus to move on the surface to be cleaned detecting obstacles and emitting signals indicative of their presence which are received by a motor control system.

Some of these apparatuses are designed for dirt and dust removal only, while other are designed for treating the surface with special substances such as detergent, deodorant, antibacterial products and the like, for example as described in WO 00/04430.

These devices are comparatively complex as far as their construction, operation and control system are

concerned and therefore their cost is too high as compared with their intended use. Moreover it is a general requirement that this type of apparatus would exhibit a power consumption as low as possible to prevent frequent operational stops for their recharge.

Summary of the Invention The object of the present invention is to provide a floor cleaning apparatus, motorized and autonomously operated, capable of performing, at the same time, the removal of dirt and dust and providing the detersion of the surface to be cleaned, while reducing to a minimum the electric power consumption and requiring an effective and inexpensive control system.

Another object of the present invention is to provide an apparatus of the above-mentioned type able to pass around any obstacle it may contact during its movement and to change its movement direction when encountering a discontinuity on the floor.

A further object of the present invention is to provide an apparatus of the above-mentioned type equipped with a device for treating the surface to be cleaned with a detergent liquid which is able to stop the detersion operation when crossing prefixed portions of said surface, in particular those covered by a carpet.

A further object of the present invention is to provide a method for cleaning floors and a method for controlling the operation of the cleaning device of the above-mentioned type which allow the electric power consumption to be minimized and various operating modes to be optimized.

A particular object of the present invention is to provide a method for cleaning floors and a control method

of the above-mentioned type wherein the operation according to different operating modes is allowed as well as the automatic passage from one to another one, wherein the cleaning of a room can be automatically stopped after a prefixed time and started a search mode for finding a passage toward a room still to be cleaned, and wherein a recharge station can be automatically reached, all these functions being performed with the aim of optimizing the apparatus performances.

The above objects are reached with the vacuum cleaning apparatus for floors according to the present invention, with the relevant method for controlling its operation and the method for cleaning floors which can be carried out thereby, the essential features of which are set forth in claims 1,11 and 16. Further advantageous features are set forth in the dependent claims.

Description of the drawings Further features and the advantages of the vacuum cleaning apparatus according to the present invention will become more apparent from the following description of an exemplifying, non-limiting embodiment thereof, made with reference to the attached drawings, wherein: - Figure 1 is a plan view of the apparatus according to the present invention, the external body thereof being removed for clarity; - Figure 2 is a side view of the apparatus of figure 1; - Figure 3 is a longitudinal sectional view taken along lines II-II of the apparatus of figure 1; - Figure 4 is a plan sectional view of the apparatus of the invention according to lines IV-IV of figure 2; - Figures 5 and 6 are front and rear perspective

assembly views of the apparatus according to the invention; - Figure 7 is a perspective view of the apparatus of the invention with the relevant external body; - Figures 8a and 8b schematically show a collision detector of the electromechanical type in normal operating condition and in a contact condition respectively; - Figure 9 is a block flow diagram showing the operating mode in case of a collision or a detection of a discontinuity; - Figure 10 is a block flow diagram showing the operating mode in case of detection of a carpet; - Figure 11 is a block flow diagram showing the operating mode in case of detection of a low battery charge level.

With reference to figures 1-6,1 denotes a box-like frame of the apparatus mounted on a pair of rear wheels 2 driven by independent electric motors 3 axially arranged and fixed to frame 1, whereby wheels 2 are both independently driven. Frame 1 is supported at its front end by a pair of wheels 10 fixed to frame 1 in an articulated way on respective vertical axes 10a.

A pair of rechargeable batteries 4 is located on frame 1 and over motors 3 of wheels 2 and before batteries 4 a third motor 5 is longitudinally located for driving a fan 6 situated in a substantially central position on frame 1. Fan 6 is in a suction engagement with a chamber 7, in which a conventional, air permeable, filtering bag 8 for dust collection is arranged. Bag 8 communicates with a conduit 9 for sucking any dirt from the floor, and suction inlet 9a thereof ends at the underside of frame 1 and faces toward the floor. Suction inlet 9a is placed before

a brush collector 13 extending side-to-side of frame 1 and having a substantially V-shaped, very spreaded outline so as to collect dirt during the movement of the apparatus and convey it toward its middle portion before which suction inlet 9a is placed. Bag 8 is accessible for replacement from the lower side of frame 1, by removing a cover 1, from which suction inlet 9a protrudes.

A plate 11 is located under frame 1 at an intermediate position. Plate 11 bears a cleaning cloth, not shown, for example of the type conventionally shaped like a cap to allow it to be manually secured to plate 11.

Plate 11 is hang to frame 1 by means of two pairs of stems 12 slidably mounted in tubular seats la of frame 1 formed at both sides thereof. Plate 11 and the relevant cloth can freely lean on the floor by virtue of its own weight or, preferably, elastic means (not shown) can be provided between plate 11 and frame 1 to ensure a moderately forced contact with the floor. Advantageously the perimetrical edges of plate 11 are bent toward frame 1 both to make easier the application of the cleaning cloth and to assist in overcoming small obstacles of the floor without the risk that plate 11 would jib against them.

A small tank 30 for sanitizing liquid, detergent or the like is located at rear side of frame 1 and is connected to a dispensing pump 31 through a pipe not shown. Pump 31 dispenses liquid on the cleaning cloth, continuously or stepwise, through holes or slits not shown formed on plate 11.

Preferably, tank 30 is made of transparent material so that the level of liquid may be checked through a window 31 formed at the rear side of frame 1. Tank 30 may be filled in through a cap 33, which can also be formed by

a capsule containing a dosed amount of detergent or other substance to be solubilized in water when necessary.

Plate 11 is centrally provided with a connection member lla connected to stem 23a of an electro-magnet 23, by means of a bracket 24 in the present embodiment, located between motor 5 and batteries 4. As a result of a suitable electric signal to the electromagnet, plate 11 can be lowered and raised as required, as better explained hereinafter.

The bottom side 1b of frame 1 is formed with a plurality of slits 34 through which the air sucked by fan 6 comes out and is projected on the treated surface, thus assisting in its drying.

The system for driving the apparatus is assembled on a circuit board 35 which also includes a microprocessor implemented with a management software that can be updated through serial connection 36 placed on a control panel, generally indicated at 37, arranged on frame 1 and comprising a display 38, a control keyboard 39 and an instruction board 40.

The apparatus further comprises an outer body 41, shown in figure 7 by way of example, elastically fixed to frame 1. Outer body 1 conceals the frame and rear wheels and is provided with a transparent cover 42 to have access to control panel 37.

The apparatus according to the invention is equipped with three groups of sensors which have the task to control the movements thereof. A first sensor is formed by a collision sensor 15, for example of the magnetic type, formed by a switch 18 operated by a magnet, not shown, fixed to body 41 correspondingly. As a result of a collision of the body with an obstacle and thanks to the

elastic connection of body 41 to frame 1, the displacement of body 41 moves the magnet away from switch 18 and opens the electric circuit on which switch 18 is mounted. As an alternative, collision sensor 15 may be of the electro- mechanical type. As shown in figures 8a and 8b, the collision sensor 15 comprises an angled bracket 16 having a free end 16a which is fixed to body 14, while the other end 16b is linked to box 15a of sensor 15. By means of a spring 17 angled bracket 16 is forced against a switch 19.

In this case a pair of collision sensors 15 is provided preferably located on frame 1 approximately above rear wheels 2. Figure 8a illustrates the condition of normal operation, while figure 8b represents the situation occurring when body 41 bumps against an obstacle. The resulting cut-off of the electric current associated to switch 18 or 19 constitutes a signal which is processed in the electronic control system of the apparatus to provide motors 3 with a selective control signal to immediately stop the forward motion of the apparatus as described hereinafter.

As an alternative, infrared proximity sensors may be used as collision sensor, arranged along body 41 to be activated before the apparatus bumps against an obstacle.

A second sensor, which the apparatus is equipped with, is intended for detecting low obstacles, i. e. surmountable by the apparatus as being of a thickness lower than the minimum distance of the body from the floor In the example shown in figure 1 the second sensor comprises a pair of infrared proximity sensors 20 mounted on a bracket 21 extending frontwise from frame 1. Sensors 20 detect, in particular, the presence of a carpet and can activate a lifting movement of plate 11 to prevent the

cloth applied to it from coming into contact with the carpet either as soaked with detergent substances or to avoid an excessive friction.

A third group of sensors, which the apparatus is equipped with, has the function to detect any floor discontinuity consisting of lack of supporting surface, such as a step. In the present embodiment of the invention two discontinuity sensors 22 are provided, which are fixed on bracket 21 at the outside of sensors 20 before front wheels 10. Sensors 22 are infrared proximity sensors onwardly oriented and downwardly inclined, while sensors 20 are vertically downward directed.

For example, in the presence of an approaching step, sensors 22 emit a signal for starting a stop procedure of the apparatus forward motion as explained later on.

The apparatus can be manually or automatically connected to a battery recharge unit, not shown. In the first case, the apparatus is on during the recharge, but, once it is charged and disconnected, a start and, possibly, pause button must be pressed to start it. In the second case, once the batteries are charged, the apparatus automatically starts.

The apparatus moves always straight forward at a preset speed and with the suction system on or off and capable of temporarily being started in case of a collision only, so as to reduce noise and energy consumption.

The operating control modes of the apparatus according to the invention are essential to the aim of achieving the objects of the invention. The operating sequence of the various operating conditions is shown in the flow diagrams of figures 9,10 and 11.

The apparatus is programmed for a combined random/spiral operating mode, to minimize the number of passages on the same surface portion without leaving untreated surface portions in the stated period of time of permanence in a certain room. The passage from a random operating mode to a spiral operating mode is decided when the time interval At between two successive bumps exceeds a prefixed value tu.

In figure 9 there is shown the operating mode when a bump occurs or a surface discontinuity due to a stair step is detected. The apparatus reacts to the signal generated by such event in a different way according to the operating program which is active at that time. More particularly, if the signal is emitted after a time At has elapsed greater or equal to a prefixed time tu from the last discontinuity or bump signal, the spiral operating mode is started, whereby the emission of the signal results in the apparatus stop, a 180° rotation and a forward motion for a time equal to At/2, after which the apparatus stops again and begins to move with a spiral motion. In practice, in this way the apparatus starts the spiral motion approximately from the middle of the segment uniting the last two encountered obstacles. If the bump or the discontinuity due to a stair step are detected when the apparatus is already in the spiral operating mode, the apparatus stops and performs a 90° rotation to start the random operating mode passing along a radial trajectory through the center of the spiral followed up to that time.

In the case of a bump in the random operating mode, the forward motion of the apparatus is stopped and started a rearward motion for a prefixed time Tr, at the end of which the apparatus stops again and performs a rotation of

a random angle 8 comprised between two prefized end values 81 and 82 (for example between 60° and 160°). Afterwards, the apparatus starts again in the random operating mode.

The rotation of the angle 8 always occurs in the same direction, until it is denied by the presence of an obstacle; from this time on the rotation always occurs in the opposite direction, until it is denied by a new obstacle.

In this case, unless the silent operating mode is on, during the time Tr of the rearward motion the fan is activated for the removal of the dirt and is shut off at the end of the rearward motion.

As a last case, the collision or detection of the discontinuity due to a stair step can occur when the room change operating mode has been activated, i. e. when a time T greater than time Tc of permanence in the same room has elapsed. In this case the apparatus stops, performs a rotation of an angle a comprised between 90 and 180°, in particular 135°, and starts again running along a closed curvilinear trajectory, in particular a repeated semi- circular trajectory. If the last bump was against a wall, it repeats the sequence at each subsequent bump against the same wall while performing semicircular trajectories, until a doorway is reached and the trajectory arc P is greater than 180°, this being further increased of an angle y comprised between 30° and 90° up to a total angle of 270° maximum, after which the apparatus begins to clean the new room it has reached.

Figure 10 shows the operating mode when the apparatus encounters a carpet. If the apparatus is programmed to work in the silent mode or in a mode which does not include the carpet cleaning operation, the carpet

detection signal is considered as an obstacle detection signal, i. e. a collision signal, and handled as previously described. Instead, if the carpet cleaning function is active, plate 11 is lifted, the dispensing of the detergent liquid is interrupted and suction is started, before keeping on working on the carpet in the standard work conditions. Leaving the carpet can be detected via software in a conventional heuristic way or by means of a dedicated proximity sensor.

When the charge level of the batteries goes below a prefixed value, the room change mode is started and the apparatus reaches the first available doorway (Fig. 11).

If the apparatus is manually rechargeable, it stops immediately at the doorway and emits an alarm signal. If the apparatus is automatically rechargeable, the apparatus keeps on running along the walls according to the room change mode until the guide of the recharge station is found on the floor surface. Once the guide has been found, the apparatus aligns itself thereon and follows it until it enters the recharge station. The guide is formed by a strip of plastic material extending on the floor for some length from the recharge station and embodying a conductor wherein a current flows. The contacts for the recharge can be located in a suitable position on the top side of the external body or on the sides thereof. The apparatus is provided with a suitable sensor, not shown, for detecting the conductor of the guide and emitting a signal which is sent to the apparatus driving system.

The driving system controls the speed of the apparatus as a function of the frequency of the collision/discontinuity signals which are generated, whereby the speed is increased after a prefixed time from

the last received signal has elapsed. Likewise, if the bumps become too frequent, the selection range for random angle 8 is properly reduced.

In order to make easier the movements of the apparatus according to the invention, it may be equipped with a remote control (for example, of the joy-stick type) by means of which it is possible to transfer it to the working area, without the need of carrying it there, or even to interrupt its operation at any time.

Several variations and modifications can be brought to the floor cleaning apparatus according to the invention. In particular, there can be used sensing devices both of a collision and a floor discontinuity which are different from those used in the above described embodiment of the invention and selected by virtue of their structural simplicity and low cost only. Likewise, the arrangement of the various components on the apparatus frame may be varied with respect to that shown above as a function of the apparatus design which can limit the space availability. The external shape of the apparatus may also be varied without changing the innovative concept of the invention. These and other modifications which may be brought to the floor cleaning apparatus according to the present invention fall within the scope of the invention as set forth in the annexed claims.