WO2015159238A1

WO2015159238A1 - Device for cleaning angled surfaces

Info

Publication number: WO2015159238A1
Application number: PCT/IB2015/052750
Authority: WO
Inventors: Massimo Carli
Original assignee: Solebrilla Srl
Current assignee: Solebrilla Srl
Priority date: 2014-04-16
Filing date: 2015-04-15
Publication date: 2015-10-22
Anticipated expiration: 2016-10-16

Abstract

Described is a device for cleaning angled surfaces, comprising a frame (2), retaining means (18) associated with the frame (2) and configured to allow the positioning of the device above a surface to be cleaned, cleaning means (3) rotatably associated with the frame (2) and at least partly extending below it to generate a rubbing action on the surface to be cleaned, supporting means (4) associated with the frame (2), projecting below it and configured to distance the frame (2) from the surface to be cleaned and feed means (5) rotatably associated with the frame (2) for rotating relative to it and to the surface to be cleaned causing the frame (2) to be moved along an operating direction (A). The cleaning means (3), the supporting means (4) and the feed means (5) are at least partly defined by a first brush (6) and a second brush (7) rotatably connected to the frame (2) to rotate about respective axes of rotation (B, C).

Description

DESCRIPTION

DEVICE FOR CLEANING ANGLED SURFACES

Technical field

This invention relates to a device for cleaning angled surfaces, in particular for cleaning photovoltaic panels in situ.

More specifically, this invention is applied in particular in the renewable energy sector, and in particular in the routine and extraordinary maintenance of the systems.

Background art

There are numerous prior art devices for cleaning photovoltaic panels, which can be divided mainly into two categories, self-propelled, and not (nozzles, brushes etc.).

The self-propelled devices currently known are all equipped with a frame to which suitable rubbing brushes are rotatably coupled, which may be cup-shaped (that is, rotatable about a vertical axis) or roller-shaped (that is, rotatable about a horizontal axis).

To allow the movement of the device, all the prior art devices are equipped with supporting and feeding means, which are generally defined by a plurality of motor-driven wheels, rotatable directly on the surface to be cleaned or, in the majority of cases, coupled to suitable guides or rails outside the photovoltaic panel so as not to ruin it.

Disadvantageously, these solutions are particularly onerous from both the installation and economic points of view, because they are linked to the presence of means for retaining the device to be installed before the cleaning activities and, often, to be kept in situ even if not used.

Moreover, it should be noted how the need to couple and uncouple the device from each panel (or group of panels) at the start and at the end of each cleaning operation results in considerable rigidity for the operations and, consequently, a reduction in efficiency in terms of time and costs. Further, the need to provide the device with special motors both for the movement and for the rotation of the brushes forces the designer to considerably increase the weight of the device.

Obviously, as these devices are designed for use on angled surfaces or on roofs, the weight of the device becomes a very important factor and an increase in the weight might prove decisive for the safety and for the comfort the operators.

Disclosure of the invention

The aim of this invention is to provide a device (self-propelled) for cleaning angled surfaces which is able to overcome the above-mentioned drawbacks of the prior art.

More specifically, the aim of this invention is to provide a device (self- propelled) for cleaning angled surfaces which has high performance levels which allows a continuity in the operating to be guaranteed.

Moreover, the aim of this invention is to provide a device (self-propelled) for cleaning angled surfaces which guarantees maximum safety for the operators and is very easy to handle.

These aims are achieved by a device for cleaning angled surfaces according to one or more of the subsequent claims, and in particular by a device comprising a frame, retaining means associated with the frame and configured to allow the positioning of the device above a surface to be cleaned, cleaning means rotatably associated with the frame and at least partly extending below it to generate a rubbing action on the surface to be cleaned, supporting means associated with the frame, projecting below it and configured to distance the frame from the surface to be cleaned and feed means rotatably associated with the frame for rotating relative to it and to the surface to be cleaned causing the frame to be moved along an operating direction, wherein the cleaning means, the supporting means and the feeding means are at least partly defined by a first and a second brush rotatably connected to the frame for rotating about respective axes of rotation (in use substantially parallel with the surface to be cleaned) oriented in such a way as to define the feed direction.

According to one aspect of the invention, the device is equipped with at least an actuator unit connected to the first and second brush and configured for rotating them in the same direction.

Preferably, the actuator unit is configured for imparting different angular speeds to the first and second brushes in order to reduce the speed of travel of the device, thus increasing rubbing action.

Moreover, this allows the slower brush (in use, preferably the rear brush) to grip the surface during passage of the device from one panel to the adjacent one, that is, when the faster brush (in use, preferably the front brush) tends to slide on any differences in level, thus losing traction.

Brief description of drawings

These and other features are more apparent from the detailed description, set out below, of a preferred non-limiting example embodiment of a device (self-propelled) for cleaning angled surfaces as illustrated in the accompanying drawings, in which:

- Figure 1 is a schematic exploded view of a device for cleaning angled surfaces according to this invention;

- Figure 1 a shows a detail of an accessory of the device of Figure 1 ;

- Figure 2 is a schematic plan view of the device of Figure 1 , with a different set up;

- Figure 2a shows a detail of the device of Figure 2;

- Figures 3a and 3b show the device of Figure 1 in a operating step;

- Figure 4 shows a view corresponding to the cross-section IV - IV of Figure 2;

- Figures 4a and 4b show two details of Figure 4;

- Figures 5a to 5d show different views of a second embodiment of the device for cleaning angled surfaces according to this invention; - Figures 6 and 7 are schematic perspective views of a third and a fourth embodiment of the device for cleaning angled surfaces according to this invention;

- Figure 8 is a schematic view of the device for cleaning angled surfaces according to this invention during use.

Detailed description of preferred embodiments of the invention

With reference to the accompanying drawings, the numeral 1 denotes a device for cleaning angled surfaces according to this invention.

Preferably, these angled surfaces, forming the surface to be cleaned, are photovoltaic panels "SP" installed on the roofs of buildings or supported by special inclinable structures in "photovoltaic fields or parks" or the like. The device 1 comprises a supporting frame 2 from which extend the functional elements of the device. This frame 2 is preferably tubular.

In the preferred embodiment, the frame 2 has a main portion 2a, on which are positioned the drive units, the control unit and the wiring (and the battery if present), and at least two forks 2b extending from the main portion 2a.

Preferably, the main portion 2a is located in a central position and the two forks extend from it with opposite orientations.

Thus, preferably, the frame 2 is substantially in the shape of an "H".

The device 1 also comprises cleaning means 3 rotatably associated with the frame 2, and in particular with the forks 2b, at least partly extending below it to generate a rubbing action on the surface to be cleaned.

In order to maintain the distance between the surface and the frame 2, the device 1 also comprises supporting means 4, associated with the frame 2 and protruding below it.

There are also feed means 5 rotatably associated with the frame 2 for rotating relative to it and relative to the surface to be cleaned, causing the frame 2 to be fed along a line of operation "A". Preferably, the cleaning means 3, the supporting means 4 and the feed means 5 are all at least partly defined by a first brush 6 and a second brush 7 rotatably connected to the frame 2 to rotate about respective axes of rotation "B", "C" oriented in such a way as to define the feed direction (A).

Preferably, the axes of rotation "B", "C" are, in use, substantially parallel with the surface to be cleaned.

Moreover, in the embodiment illustrated, the axes of rotation "B", "C" are substantially parallel to each other.

More specifically, the axes of rotation "B", "C" of the brushes 6, 7 are at right angles to the operating direction "A".

In other words, the frame 2 is provided with two rotatable brushes 6, 7 (or rollers) protruding downwards in such a way that the weight of the device is discharged onto the surface to be cleaned through the periphery of the brushes themselves.

In that way, during the rotation of the brushes 6, 7, a friction force is generated with the surface which determines a forward movement of the device along the operating direction "A" (orthogonal to the axes of rotation of the brushes 6, 7) and a corresponding rubbing of the brushes on the surface.

Advantageously, in this way it is not necessary to provide for the use of specific movement means distinct from the cleaning means, with considerable advantages both in the simplicity and the lightness of the device 1.

Preferably, the brushes 6, 7 are pivoted onto the forks 2b of the frame 1 , on opposite sides relative to the main portion 2a.

It should be noted that the operating direction "A" corresponds to a line joining the two axes of rotation "B" the brushes 6, 7, preferably at right angles to both. Thus, during operation, the first brush 6 and the second brush 7 can be defined as the front brush and the rear brush, or vice versa, depending on their direction of rotation.

In this regard, it should be noted that the device 1 comprises at least one actuator unit 8 connected to the first brush 6 and to the second brush 7 and configured to rotate them in the same direction.

In other words, the actuator unit 8 comprises a motor 9 and at least one transmission system 10 configured for imparting to the brushes 6, 7 a rotation having a same direction.

Advantageously, in this way the slower brush can maintain its grip on the surface also during the passage of the device 1 above an obstacle, for example in the transit from one panel "SP" to the adjacent one, that is, when the faster brush tends to slide on any differences in level, thus losing traction.

Preferably, the actuator unit 8 is configured to impart to the first brush 6 and to the second brush 7 angular speeds which are different to each other.

In other words, the first brush 6 and the second brush 7, in use, rotate at different speeds.

Advantageously, in this way the brush which rotates at a slower speed (slow brush) tends to slow down the forward movement of the device imparted by the brush which rotates at a speed higher (fast brush), guaranteeing an increase in the rubbing effect on the surface and keeping control of the movement of the device 1 .

In the embodiment illustrated, the ratio between the speed of rotation of the first brush 6 and the second brush 7 is substantially constant.

Thus, irrespective of the direction of rotation, the first brush 6 rotates more quickly than the second brush 7.

Alternatively, the actuator unit 8 may be configured to impart to the first brush 6 and to the second brush 7 a first direction of rotation "θι ," defining a first direction of the operating direction "A", wherein the first brush 6 has a forward position and an angular speed greater than that of the second brush 7.

Moreover, the actuator unit 8 may be configured to impart to the first brush 6 and to the second brush 7 a second direction of rotation "Θ2," defining a second direction of the operating direction "A", wherein the second brush 7 has a forward position and an angular speed greater than that of the first brush 6.

Thus, in this embodiment, in the first direction of rotation "Θ the first brush 6 is a front brush of the device 1 , whilst in the second direction of rotation "Θ2" the first brush 6 is a rear brush of the device 1 .

In other words, in this embodiment the actuator unit 8 is configured to impart to the brushes 6, 7 a rotation such that the front brush, with reference to the operating direction "A", has an angular speed greater than that of the rear brush.

Preferably, the actuator unit 8 comprises a motor 9 connected to the frame 2 (preferably fixed to the main portion 2a).

The motor 9 is connected to the first brush 6 and to the second brush 7 by a transmission system 10 equipped with at least a first chain 10a and a second chain 10b.

It should be noted that, alternatively, belts or the like might be used instead of the chains.

Thus, the motor 9 is provided with a shaft 9a and the chains 10a, 10b are connected to the brushes 6, 7 (in particular to the shafts of the brushes) by a set of gears.

Preferably, the actuator unit 8 (in particular the movement system 10) comprises at least one unit 1 1 for adjusting the pulling of the first chain 10a and the second chain 10b.

This adjusting unit 1 1 is configured to allow an operator to vary the relative position between the shaft 9a of the motor 9 and the axis of rotation "B" (that is, the shaft) of the first brush 6 and second brush 7. In this regard, preferably, the motor 9 is connected to the (transmission) shaft 9a by a compliant joint which is able to allow a movement or an inclination of the shaft 9a.

The adjusting unit 1 1 comprises a contact element 1 1 a movable transversely to the shaft 9a for translating the position of the shaft radially so as to vary the pull of the first chain 10a and the second chain 10b keyed on it.

In the preferred embodiment, the contact element 1 1 a has a threading which allows a fine adjustment/movement.

The contact element 1 1 a is preferably in contact on a rotation bearing of the shaft.

In the embodiment illustrated, the contact element 1 1 a is defined by two screws vertically movable and located on opposite sides relative to the bearing for angling towards the first brush 6 or towards the second brush 7 so as to further increase the pull, respectively, of the second chain 10b or of the first chain 10a.

These screws may be operated manually or automatically.

The device 1 is preferably configured to dispense a cleaning liquid (water or detergent) on the surface to be cleaned.

The device comprises at least one duct 12 for distributing a cleaning liquid provided with at least one access opening 12a connectable to a tank or source of the liquid (preferably a water source, such as the mains) and a plurality of outlets 13, 14, 15 which are spaced from each other and distributed along at least the first brush 6.

Preferably, the plurality of outlets 13, 14, 15 comprise a predetermined number of first nozzles 13 angled towards the first brush 6 for supplying corresponding first jets "G1 " of cleaning liquid onto the first brush 6.

Moreover, the plurality of outlets 13, 14, 15 comprise a predetermined number of second nozzles 14 angled towards the surface to be cleaned for supplying corresponding second jets "G2" of liquid in a first zone Z1 of the surface to be cleaned which is immediately in front of the first brush 6 with reference to the line of operation "A".

Thus, the distribution duct 12 is formed by a tubular body extending parallel with the first brush and located in front of it.

Preferably, the duct 12 is rigidly connected to the frame 2 and extends from one arm to the other of one of the forks 2b.

In the preferred embodiment, the duct 12 is located in a position distal from the surface to be cleaned relative to the axis of rotation "B" of the first brush 6.

In the preferred embodiment, the plurality of nozzles 13, 14, 15 also comprises a predetermined number of third nozzles 15 oriented, with reference to the operating direction "A", in front of the frame 2, that is, away from the frame.

The third nozzles 15 are configured for supplying corresponding third jets "G3" of detergent liquid projecting in front of the device in a second zone "Z2" of the surface to be cleaned which is distal from the device relative to the first zone Z1.

Advantageously, in this way the duct 12 allows the distribution of the cleaning liquid in three zones, both for cleaning and cooling, since the third nozzles 15 allow the water to be dispensed on a zone of the panels "SP" at a predetermined distance from the device 1 , so that they can be cooled gradually from the start of the cleaning.

Preferably, the third nozzles 15 have a smaller cross section than that of the first nozzles 13 and second nozzles 14 to determine a vaporisation effect of the liquid.

In the preferred embodiment, the duct 12 is defined by a microperforated tube, wherein the holes define the outlet openings.

Preferably, the device 1 is provided with two ducts 12, each associated with a respective brush 6, 7.

The ducts 12 are anchored to the frame 2, in particular to the arms of the forks 2b on opposite sides of the main portion 2a.

Preferably, the ducts are rigid, made of metal, and define respective handles for lifting the device.

In the preferred embodiment, the device comprises at least two grips (not illustrated) each associated with a duct 12 to facilitate gripping and lifting the device by two operators.

Preferably, the device also comprises a third brush 16 interposed between the first brush 6 and the second brush 7 and connected to the frame 2 in such a way that it can move axially towards and away from it along a line transversal to the line of operation "A", for varying the friction force applied on the surface to be cleaned.

The third brush 16 is associated in a movable fashion with the main portion 2a of the frame 2 for moving towards and away from it.

Preferably, the third brush 16 comprises a support 16a extending parallel to the first brush 6 and second brush 7 and movably connected to the frame 2 (in particular to the main portion 2a) and a plurality of bristles 16b connected to the support 16a and each extending between a first end constrained to the support 16a and a second free end.

Preferably, the third brush 16 is brush-shaped.

Preferably, the third brush 16 is associated with the actuator unit 8 for being moved (more preferably, with a dedicated actuator 36).

Alternatively, in the embodiment illustrated, the third brush 16 can be moved manually by an operator.

In some embodiments (Figure 7), the device comprises a further brush 35, rotatably coupled to the frame, but braked or idle relative to the frame 2.

It should be noted that, to allow a correct movement of the brushes (as well as a correct dispensing of the liquids), the device is equipped with a control unit 17 operatively associated with the actuator unit 8.

The device also comprises a control interface 17a connected (preferably by flexible cable 27) to the frame 2, and in particular to the control unit 17.

The control interface 17 comprises one or more commands operatively associated with the actuator unit 8 for defining the speed and the direction of rotation of the first brush 6 and the second brush 7 and, if necessary, the position of the third brush 16.

To allow the retaining and the guiding of the device 1 , it comprises retaining means 18 associated with the frame 2.

The retaining (and guiding) means 18 are thus connected to the frame 2 and extend away from it along a line transversal to the operating direction

"A".

Preferably, the frame 2 comprises at least one connecting pocket 19 which can be removably associated with the retaining means 18.

Even more preferably, the retaining means 18 may be replaced, that is, provided with attachment means reversibly coupled with the seat 19.

In a first embodiment, the retaining means 18 comprise a rigid movement rod 20 protruding from the seat 19 away from the frame 2 along a line orthogonal to the line of operation "A".

Advantageously, in this way, the operator can vary the position of the device 1 along at least a direction at right angles to the operating direction, by pulling or releasing the rod 20.

Also, the stiffness of the rod 20 allows the operator to support the movement means 4 (that is, the brushes 6, 7) simply by exploiting the lever effect.

Preferably, the rod 20 is modular, so that it can be adapted to the size of the surface to be cleaned.

In a second embodiment, the retaining means 18 comprise a rake 21 provided with a plurality of retaining rollers 22 (or rolling elements) designed to fasten onto an upper edge of a photovoltaic panel "SP" for holding the device 1 in the operating position.

In other words, the rake 21 is shaped to retain the device at a predetermined height and the rollers 22 allow the forward movement "A" along the direction "A".

It should be noted that the rake 21 may be detachably connected to the frame 2 (Figure 1 a) or integrated in the frame 2 itself (Figures 5a to 5d), Preferably, the rake 21 is provided with two end portions 21 a, each provided with at least one of the rollers 22, the end portions being telescopically connected to a central portion 21 b of the rake 21 .

In this regard, the rake 21 is fitted with at least one lock pin 23 associated with the end portions 21 a to lock the sliding relative to the central portion 21 b in at least two predetermined positions.

Advantageously, in this way it is possible adapt the size of the rake 21 to the application, and in particular to the distance which separates two successive photovoltaic panels "SP".

In at third embodiment, the retaining means 18 comprise at least one grip 24 extending between two end portions 24a and at least a pair of control cords 25 each extending between an end portion 24a of the grip 24 and the frame 2.

More specifically, the two operating cords are connected to the frame 2 on opposite sides relative to the main portion 2a, that is, relative to a middle axis of the device.

Advantageously, in this way an operator can vary the orientation of the operating direction "A" by means of a simple rotation of the grip 24.

In other words, advantageously in this way the device 1 is controlled like a kite.

Preferably, also, the grip 24 is rotatably associated with a reel 26 equipped with two pulleys 26a on which the two operating cords 25 can be wound. It should be noted that, preferably, in all the embodiments described, the interface 17a is connected to the control unit 17 by a spiral-shaped flexible cable 27, extending around the retaining means in such a way as to reduce the spread of the components of the device 1.

Preferably, the device 1 is autonomous from an energy point of view. Thus, preferably, the device 1 comprises a battery 37 mounted on the frame 2 (that is, fixed to it) and connected to the actuator unit 8, preferably to the motor 9. In the embodiment illustrated, the battery 37 is connected to the main portion 2a of the frame 2.

It should be noted that the device comprises at least one water supply tube 28 associated with the frame 2 and extending away from it.

More specifically, the water supply tube 28 is in fluid connection with the ducts 12.

Considering the fact that the device 1 according to this invention is conceived for a use on angled surfaces, and thus under precarious conditions of equilibrium for an operator, the tube 28 defines a risk factor for the operator's safety.

In this regard, the device 1 is preferably provided with lightening means 30 constrainable to the tube 28 to reduce the weight which they discharge onto the ground favouring the movement.

Moreover (see Figure 3a), these lightening means 30 might be connected directly to the frame 2 of the device or, for example, to the rake 21 to favour their movement and the movement from a panel "SP" to the adjacent one.

In embodiments not equipped with the battery 37, the device 1 could be equipped with at least one electricity supply cable extending from the frame away from it.

In the preferred embodiment, the lightening means 30 are preferably defined by inflatable elements, preferably inflated by helium, of a size suitable for providing a lift to the tube 28 and to the cable 29.

Advantageously, this solution is simple and inexpensive to implement, making it also possible to promote the activity during the cleaning (especially if performed on roofs).

For applications on the ground, where it is necessary for the operator to position the device 1 on the panels "SP" from below, the device 1 is preferably provided with or can be provided with a raising system 31 associated with the frame 2 and designed to impart to the device a movement orthogonal to the line of operation "A", for allowing the device to be raised on an angled surface to be cleaned.

Preferably, the raising system 31 comprises a threaded bar 32 extending along its own central axis and provided at one end 32a with a grip 33 which can be grasped by an operator for rotating it.

Alternatively, the end 32a of the bar 32 could be equipped with coupling means (for example, a socket or a polygonal pin) with an automatic screwing unit, such as, for example, a drill, an electric screwdriver or the like.

Moreover, the frame 2 of the device 1 comprises at least a threaded nut 34, rigidly connected to it and able to engage with the bar 32.

In that way, a rotation of the bar 32 about its central axis corresponds to a translation of the frame 2 along the central axis.

Preferably, the threaded bar 32 has a coarse thread, so that it will withstand impact and wear.

Preferably, in order to allow an increased adaptability, the bar 32 is modular. It should be noted that the modules of the bar 32 are configured in such a way that the thread is substantially continuous at the joining point between two adjacent modules.

It should be noted that, preferably, the bar 32 is rotatably associated with a rake 21 , in such a way as to also form means for retaining the device 1 . In an alternative embodiment, the raising system comprises one or more ropes interposed between the rake 21 and the frame 2 and at least one return pulley associated with the rope (or ropes) to enable the operator to raise the device from a lower level (that is, from the base of the panels). The invention achieves the preset aims and brings major advantages. In effect, the presence of brushes or rollers defining both the cleaning means and the movement means which are able to rotate in the same direction allows the device to easily overcome the obstacles and the differences in level in the passage from one photovoltaic panel to the adjacent one.

Moreover, the different speed of rotation of the two brushes allows the rubbing action on the surface to be cleaned to be maximised, keeping control of the speed of forward movement.

Moreover, the presence of multi-directional ducts for distribution of the water allows the efficiency of the cleaning to be maximised with a minimum effort.

Another considerable advantage is due to the possibility of using a third brush movable axially so as to vary the friction force with the surface, both for cleaning and for controlling the speed.

Lastly, the presence of a coupling seat with different types of retaining means also allows the device to be adapted to all the applications and all the cleaning requirements linked to the different installations and shapes of the photovoltaic panels.

Claims

1. A device for cleaning angled surfaces, comprising:

- a frame (2);

- retaining means (18) associated with said frame (2) and designed to allow device positioning above a surface to be cleaned;

- cleaning means (3) rotatably associated with said frame (2) and at least partly extending below it to generate a rubbing action on said surface to be cleaned;

- supporting means (4) associated with the frame (2), projecting below it and designed to distance said frame (2) from the surface to be cleaned;

- feed means (5) rotatably associated with the frame (2) for rotating relative to it and relative to the surface to be cleaned, causing the frame (2) to be fed along a line of operation (A);

characterised in that said cleaning means (3), said supporting means (4) and said feed means (5) are at least partly formed by a first brush (6) and a second brush (7) rotatably connected to the frame (2) for rotating about respective axes of rotation (B, C) so as to define said line of operation (A).

2. The device according to claim 1 , characterised in that it comprises at least one actuator unit (8) connected to said first brush (6) and second brush (7) and designed to make them rotate in the same direction.

3. The device according to claim 1 or 2, characterised in that said actuator unit (8) is designed to impart different speeds of revolution to said first brush (6) and to said second brush (7).

4. The device according to any one of the preceding claims, characterised in that said actuator unit (8) comprises a motor (9) connected to the first brush (6) and to the second brush (7) by a transmission system (10) provided respectively with a first chain (10a) and a second chain (10b); said actuator unit (8) comprising at least one adjusting unit (1 1 ) for adjusting the pull of said first chain (10a) and said second chain (10b) designed to allow an operator to vary the relative position of a shaft (9a) of said motor (9) and the axis of rotation (B, C) of said first brush (6) and second brush (7).

5. The device according to any one of the preceding claims, characterised in that it comprises at least one duct (12) for distribution of a cleaning liquid provided with at least one access opening (12a) connectable to a tank or source of said liquid and also provided with a plurality of outlets (13, 14, 15) which are spaced and distributed along at least said first brush (6); said plurality of outlets () comprising at least:

- a predetermined number of first nozzles (13) angled towards said first brush (6) for supplying corresponding first jets (G1 ) of cleaning liquid onto the first brush (6);

- a predetermined number of second nozzles (14) angled towards the surface to be cleaned for supplying corresponding second jets (G2) of liquid in a first zone (Z1 ) of the surface to be cleaned which is immediately in front of the first brush (6) with reference to said line of operation (A).

6. The device according to claim 5, characterised in that said plurality of outlets (13, 14, 15) also comprises a predetermined number of third nozzles (15) angled in front of the frame (2) with reference to said line of operation (A), for supplying corresponding third jets (G3) of liquid projecting in front of the device in a second zone (Z2) of the surface to be cleaned which is distal from the device relative to said first zone (Z1 ).

7. The device according to claim 5 or 6, characterised in that said distribution duct (12) is formed by a tubular body extending parallel with said first brush (6) and located in front of it, in a position distal from the surface to be cleaned relative to the axis of rotation (B) of the first brush

(6).

8. The device according to any one of the preceding claims, characterised in that it comprises a control unit (17) operatively associated with the actuator unit (8) and a control interface (17a) connected to the control unit (17); said interface (17a) being connected to the control unit (17) by a spiral flexible cable (27), extending around the retaining means (18) in such a way as to reduce the spread of the components of the device.

9. The device according to any one of the preceding claims, characterised in that it comprises a third brush (16) interposed between said first brush (6) and second brush (7) and connected to the frame (2) in such a way that it can move axially towards and away from it along a line transversal to said line of operation (A), for varying the friction force applied on the surface to be cleaned.

10. The device according to any one of the preceding claims, characterised in that said retaining means (18) are reversibly coupled with a connecting seat (19) made in said frame (2) using suitable connecting means.

1 1 . The device according to any one of the preceding claims, characterised in that the retaining means (18) comprise a rigid movement rod (20) protruding from said seat (19) away from the frame (2) along a line orthogonal to said line of operation (A).

12. The device according to any one of the preceding claims, characterised in that the retaining means (18) comprise a rake (21 ) provided with a plurality of retaining rollers (22) designed to fasten onto an upper edge of a photovoltaic panel (SP) for holding the device in the operating position.

13. The device according to claim 12, characterised in that said rake (21 ) is provided with two end portions (21a), each provided with at least one of said rollers (22), the end portions being telescopically connected to a central portion (21 b) of the rake (21 ).

14. The device according to any one of the preceding claims, characterised in that the retaining means (18) comprise at least one grip (24) extending between two end portions (24a) and at least a pair of control cords (25) each extending between an end portion (24a) of the grip (24) and the frame (2) for allowing an operator to vary the orientation of said line of operation (A) by rotating the grip (24).

15. The device according to any one of the preceding claims, characterised in that it comprises lightening means (30) constrainable to a water feed tube (28) and/or to the frame (2) and/or to the retaining means (18) for the weight that they discharge onto the ground, promoting their movement.

16. The device according to any one of the preceding claims, characterised in that it comprises a raising system (31 ) associated with the frame (2) and designed to impart to the device a movement orthogonal to said line of operation (A), for allowing the device to be raised on an angled surface to be cleaned.

17. The device according to claim 16, characterised in that said raising system (31 ) comprises:

- a threaded bar (32) extending along its own central axis, provided at one end (32a) with a grip (33) which can be grasped by an operator or with means for coupling with an automatic screwing unit;

- at least one threaded nut (34) rigidly connected to the frame (2) and able to engage with said bar (32) in such a way that a rotation of the bar (32) about its own central axis corresponds to a translation of the frame (2) along said central axis.