The invention relates to a surface washing system, comprising a frame and a washing unit for washing a substantially flat surface, such as a solar panel or a window; wherein said frame comprises first and second elongated and mutually parallel guides to be mounted at two spaced apart parallel sides of said surface; wherein said washing unit is mounted to said guides by respective first and second sliders on said respective first and second guides and by first actuator means in such a manner that said washing unit is movable between said guides in longitudinal direction of said guides; wherein said washing unit is mounted to said guides by second actuator means in such a manner that said washing unit is movable between said guides in lateral direction of said guides.

The invention in particular relates to a surface washing system which is designed to be installed to clean large surfaces, which may have different sizes in each instance. The system is in particular aimed at large “solar farms”, which may comprise a large amount of photovoltaic solar panels arranged in a field in PV-arrays of tens or hundreds meters long. In order to maximize the power generated by the solar panels, it is important that the surface of the panels is regularly cleaned from dirt.

The goal of the invention is a system for cleaning surfaces such as solar panels or windows, which is reliable, cost effective, and/or which can be easily adapted to be installed for different sizes of the surfaces to be cleaned.

According to a first aspect of the invention said system comprises a water hose and or a power cable for supplying water and or electrical power to said washing unit from an external water and or power source; wherein said water hose and or power cable is/ are fixed between a first outer end of a first one of said guides and said washing unit and has a fixed length there between which is substantially equal to the sum of the longitudinal distance between the outer ends of the guides and the lateral distance between the guides, wherein said water hose and or power cable is/are routed in a first longitudinal direction from said first outer end, over a first longitudinal pulley which is movable in said longitudinal direction, and from said first longitudinal pulley towards said first slider in a second longitudinal direction along said first guide which is opposite to said first longitudinal direction, and wherein said water hose and/or power cable is/are routed from said first slider in a first lateral direction, over a first lateral pulley which is movable in said lateral direction, and from said first lateral pulley towards the washing unit in a second lateral direction which is opposite to said first lateral direction; wherein a first tension wire is fixed between a second outer end of said first guide and said first slider and has a fixed length there between, wherein said first tension wire is routed from said second outer end, over a second longitudinal pulley which is fixed to said first longitudinal pulley, and from said second longitudinal pulley to a third longitudinal pulley which is fixed to said second outer end, and from said third longitudinal pulley to a fourth longitudinal pulley which is fixed to said first outer end, and from said fourth longitudinal pulley to said first slider; and wherein a second tension wire is fixed between said second slider and said washing unit and has a fixed length there between, wherein said second tension wire is routed from said second slider, over a second lateral pulley which is fixed to said first lateral pulley, and from said second lateral pulley to a third lateral pulley which is fixed to said second slider, and from said third lateral pulley to a fourth lateral pulley which is fixed to said first slider, and from said fourth lateral pulley to said washing unit. Preferably said system comprises both the said water hose for supplying water to said washing unit from an external water source and the said power cable for supplying electrical power to said washing unit from an external power source, wherein said water hose and said power cable extend substantially parallel to each other.

By the above construction, the frame with the water hose and the power cable can easily be made to any length and width, without the routing of the hose and cable being a problem, and by arranging the hose and power cable parallel to each other, the strength of the power cable prevents the water hose from being stretched.

Preferably said water hose and said power cable extend over respective different ones of said first longitudinal and first lateral pulleys, wherein the first longitudinal pulley for the water hose and the first longitudinal pulley for the power cable are fixed to each other, and the wherein the second longitudinal pulley for the water hose and the second longitudinal pulley for the power cable are fixed to each other.

Preferably said first lateral pulley is mounted on a third slider on said first guide such that it is movable along said guide.

Preferably said water hose and/or power cable is/are fixed to said first slider, and extend(s) therefrom in said longitudinal direction towards the first longitudinal pulley and in said lateral direction towards the first lateral pulley.

Preferably the washing unit comprises at least one electrically powered motor for driving said first actuator means, said second actuator means and or one or more movable brushes of said washing unit, wherein said motor is powered by said electrical cable. Preferably said power cable is a copper cable. Preferably said water hose is a flexible plastic hose.

The invention also relates to a solar panel or window provided with a surface washing system. In particular the invention also relates to a solar panel provided with a surface washing system, wherein said solar panel extends at an angle with a horizontal plane, and wherein the guides extend along the respective top and bottom sides of the solar panel.

Preferably the length of the solar panel in horizontal direction is a multitude of the length in the direction perpendicular thereto.

The invention also relates to a method for mounting a surface washing system to a substantially flat surface, such as a solar panel or a window, said method comprising the steps of: mounting a frame comprising first and second elongated and mutually parallel guides at two spaced apart parallel sides of said surface; mounting a washing unit to said guides by respective first and second sliders on said respective first and second guides and by first actuator means in such a manner that said washing unit is movable between said guides in longitudinal direction of said guides; wherein said washing unit is mounted to said guides by second actuator means in such a manner that said washing unit is movable between said guides in lateral direction of said guides; providing a water hose and/or a power cable which has a fixed length which is substantially equal to the sum of the longitudinal distance between the outer ends of the guides and the lateral distance between the guides for supplying water and/or electrical power to said washing unit from an external water and or power source; fixing said water hose and or power cable between a first outer end of a first one of said guides and said washing unit, wherein said water hose and or power cable is/are routed in a first longitudinal direction from said first outer end, over a first longitudinal pulley which is movable in said longitudinal direction, and from said first longitudinal pulley towards said first slider in a second longitudinal direction along said first guide which is opposite to said first longitudinal direction, and wherein said water hose and/or power cable is/are routed from said first slider in a first lateral direction, over a first lateral pulley which is movable in said lateral direction, and from said first lateral pulley towards the washing unit in a second lateral direction which is opposite to said first lateral direction; fixing a first tension wire which has a fixed length between a second outer end of said first guide and said first slider, wherein said first tension wire is routed from said second outer end, over a second longitudinal pulley which is fixed to said first longitudinal pulley, and from said second longitudinal pulley to a third longitudinal pulley which is fixed to said second outer end, and from said third longitudinal pulley to a fourth longitudinal pulley which is fixed to said first outer end, and from said fourth longitudinal pulley to said first slider; and fixing a second tension wire which has a fixed length between said second slider and said washing unit, wherein said second tension wire is routed from said second slider, over a second lateral pulley which is fixed to said first lateral pulley, and from said second lateral pulley to a third lateral pulley which is fixed to said second slider, and from said third lateral pulley to a fourth lateral pulley which is fixed to said first slider, and from said fourth lateral pulley to said washing unit.

According to a second aspect of the invention said washing unit comprises: a washing frame; a rotatable disc shaped central brush mounted on said washing frame which is arranged to engage said flat surface to be washed and driven to be rotated around its axis, wherein the axis of said central brush is perpendicular to said longitudinal and lateral directions; at least one first cylindrical lateral brush, at least one second cylindrical lateral brush, at least one third cylindrical lateral brush and at least one fourth cylindrical lateral brush mounted on said washing frame, which are arranged to engage said flat surface to be washed and driven to be rotated around their respective axes, which lateral brushes extend adjacent said central brush at four different sides thereof, wherein the respective axes of said first and second lateral brushes are parallel to said longitudinal direction, and the respective axes of said third and fourth lateral brushes are parallel to said lateral direction.

By this arrangement of the brushes, the system can effectively clean large surfaces, while also reaching the outer corners of the surfaces.

Preferably said lateral brushes are arranged on a square circumference around said central brush, wherein said lateral brushes are arranged at least adjacent the four corners of said square.

Preferably said central brush and said lateral brushes are mutually coupled, for instance by means of gear wheels, such that all said brushes are forced to rotate around their respective axes if one of said brushes is driven.

Preferably the central brush is driven by a motor and the lateral brushes are driven by rotation of the central brush.

Preferably the lateral brushes comprise a pair of first cylindrical lateral brushes, a pair of second cylindrical lateral brushes, a pair of third cylindrical lateral brushes and a pair of fourth cylindrical lateral brushes mounted on said washing frame, wherein the two brushes of each pair of brushes is spaced apart and a lateral driving gear is mounted between the two brushes of said pair of brushes, said lateral driving gear engaging the central brush and an outer end of each of the brushes of said pair of brushes.

The invention also relates to a washing unit comprising: a washing frame; a rotatable disc shaped central brush mounted on said washing frame which is arranged to engage a flat surface to be washed and driven to be rotated around its axis, wherein the axis of said central brush is perpendicular to said longitudinal and lateral directions; at least one first cylindrical lateral brush, at least one second cylindrical lateral brush, at least one third cylindrical lateral brush and at least one fourth cylindrical lateral brush mounted on said washing frame, which are arranged to engage said flat surface to be washed and driven to be rotated around their respective axes, which lateral brushes extend adjacent said central brush at four different sides thereof, wherein the respective axes of said first and second lateral brushes are parallel to said longitudinal direction, and the respective axes of said third and fourth lateral brushes are parallel to said lateral direction.

The invention also relates in a third aspect to a surface washing system, comprising a frame and a washing unit for washing a substantially flat surface, such as a solar panel or a window, wherein said frame comprises first and second elongated and mutually parallel guides to be mounted at two spaced apart parallel sides of said surface, wherein said washing unit is mounted to said guides by respective first and second sliders on said respective first and second guides and by first actuator means in such a manner that said washing unit is movable between said guides in longitudinal direction of said guides, wherein said washing unit is mounted to said guides by second actuator means in such a manner that said washing unit is movable between said guides in lateral direction of said guides, wherein said system comprises a water hose for supplying water to said washing unit from an external water source, wherein said washing unit comprises: a washing frame, a rotatable disc shaped central brush mounted on said washing frame which is arranged to engage said flat surface to be washed and driven to be rotated around its axis, wherein the axis of said central brush is perpendicular to said longitudinal and lateral directions, at least one first cylindrical lateral brush, at least one second cylindrical lateral brush, at least one third cylindrical lateral brush and at least one fourth cylindrical lateral brush mounted on said washing frame, which are arranged to engage said flat surface to be washed and driven to be rotated around their respective axes, which lateral brushes extend adjacent said central brush at four different sides thereof, wherein the respective axes of said first and second lateral brushes are parallel to said longitudinal direction, and the respective axes of said third and fourth lateral brushes are parallel to said lateral direction. Optionally, in the surface washing system, said lateral brushes are arranged on a square circumference around said central brush, wherein said lateral brushes are arranged at least adjacent the four corners of said square.

Optionally, in the surface washing system, said central brush and said lateral brushes are mutually coupled, for instance by means of gear wheels, such that all said brushes are forced to rotate around their respective axes if one of said brushes is driven. Preferably, the central brush is driven by a motor and the lateral brushes are driven by rotation of the central brush. Further preferably, the lateral brushes comprise a pair of first cylindrical lateral brushes, a pair of second cylindrical lateral brushes, a pair of third cylindrical lateral brushes and a pair of fourth cylindrical lateral brushes mounted on said washing frame, wherein the two brushes of each pair of brushes is spaced apart and a lateral driving gear is mounted between the two brushes of said pair of brushes, said lateral driving gear engaging the central brush and an outer end of each of the brushes of said pair of brushes.

The invention will be elucidated by means of a preferred embodiment, with reference to the figures, wherein:

Figure 1 is a perspective view of a surface washing system for a solar panel arrangement seen from below the solar panel;

Figure 2 is a perspective view of the surface washing system of figure 1, seen from above the solar panel;

Figure 3 is a side view of the surface washing system of figure 1 ;

Figure 4A is a plan view of the surface washing system of figure 1, seen from above the solar panel, wherein the routing of the water hose in the system is accentuated;

Figure 4Bis a plan view of the surface washing system of figure 1, seen from above the solar panel, wherein the routing of the power cable in the system is accentuated;

Figure 4C is a plan view of the surface washing system of figure 1, seen from above the solar panel, wherein the routing of the tension wires in the system is accentuated; Figure 5 A is a perspective view of the surface washing system of figure 1, seen from above the solar panel, wherein the driving mechanism for the longitudinal movement of the washing unit is accentuated;

Figure 5B is a perspective view of the surface washing system of figure 1, seen from above the solar panel, wherein the driving mechanism for the lateral movement of the washing unit and driving the brushes is accentuated; and

Figure 5C is a perspective view of the surface washing system of figure 1, seen from below the solar panel, wherein the gear mechanism for driving the brushes is accentuated.

According to the figures, a surface to be cleaned, such as the upper surface of a solar panel 1, is provided with a surface washing system. The solar panel 1, the guides 2, 3 and the distance between the guides 2, 3 in the figures is not shown to scale, in practice their sizes are much larger compared to the size of the washing unit 6 as shown.

The system comprises a frame consisting of first and second guides 2, 3 mounted in longitudinal direction along both the upper and lower edges of the solar panel 1. First and second sliders 4, 5 are mounted on the first and second guide 2, 3 respectively to be moved in the longitudinal direction along the guides 1, 2.

Between the sliders 4, 5 two parallel tooth racks 7, 8 and a rotatable rod 9 are mounted extending in a lateral direction which is perpendicular to the longitudinal direction. A washing unit 6 is mounted between the sliders 4, 5 to be moved there between in the lateral direction.

The washing unit 6 comprises a plate shaped frame 600 which is provided with two gear wheels 601, 602, which each engage a respective one of the tooth racks 7, 8, and said gear wheels 601, 602 are driven by a first electrical motor 603 by means of an appropriate transmission system comprising gears (not shown), wheels 604, 605, 607 and a belt 606, in order to drive the washing unit 6 in said lateral direction between the sliders 4, 5. As an alternative the transmission system can be comprised of tooth wheel gears, without a belt.

The washing unit is further provided with a second electrical motor 608 which rotates a sleeve 609, which sleeve 609 is rotatably mounted on the washing unit 6 and which extends and rotates around the rod 9. One outer end of the sleeve 609 is provided with radial pins, which engage a sleeve 610 which is mounted on the rod near one outer end thereof at the side of the first guide 2. When the washing unit 6 is moved towards the first guide 2 and reaches the returning point, the sleeve 609 will thereby drive the sleeve 610 and cause the rod 9 to rotate. The rod 9 drives two drive gears 401, 501 mounted on the first and second slider respectively, which gears 401, 501 engage two tooth racks 201, 301 mounted on the respective guides 2, 3 in order to move the washing unit 6 in the longitudinal direction. In this manner the washing unit 6 can be displaced by the second motor 608 in the longitudinal direction by approximately the width of the washing unit 6 before the first motor 603 moves the washing unit back and forward in the lateral direction.

Washing unit 6 further comprises a rotatable central brush 610 and rotatable lateral brushes 611, arranged on the other side of the frame 600 and arranged to engage the upper surface of the solar panel 1 to be cleaned. The central brush 610 is a disc shaped brush and rotates around its central axis which extends perpendicular to the surface to be cleaned. The 8 lateral brushes 611 are cylindrical and rotate around their central axes which extend parallel to the surface to be cleaned. The eight lateral brushes 611 extend in a square circumference around the central brush, two brushes 611 on each side of the square. The brushes 611 are mounted in brackets 612 on the frame 600. The brushes 610, 611 are interconnected by means of gears 613 so as to rotate together if the central gear is driven by the first electrical motor 603. To that end, as shown in figure 5, the back side of the central brush 610 is provided with a ring gear 616 with external gear teeth which engage the gears 613 and internal gear teeth, and the central brush 610 is driven by a central gear 614 mounted on the shaft of the wheel 607, which drives the central brush by means of planetary gears 615 which engage said internal gear teeth of the ring gear 616. The gears 613 engage the lateral brushes 611 by means of conical gears.

The washing unit further comprises a spray bar 617 with nozzles, which is mounted adjacent the brushes 611 on the top side of the washing unit. The system further comprises a water hose connected to said splray bar 617 and an electrical power supply cable connected to the first and second electrical motors 603, 608. With reference to figures 4A, 4B and 4C the routing of the water hose and the electrical power supply cable will be explained.

As shown in figure 4 A, the water hose 10 is fixed between the outer end 21 of guide 2 and the washing unit 6. The water hose 10 is routed in the longitudinal direction over a first longitudinal pulley 101 which is movable along the guide 2 in the longitudinal direction, and from said first longitudinal pulley 101 towards the a connector 402 on the slider 4. From there the water hose 10 is routed from the connector 402 on the slider 4 in the lateral direction over a first lateral pulley 102 which is movable the lateral direction, and from said first lateral pulley 102 towards a connector 618 on the washing unit 6, which is connected to the spray bar 617. As shown in figure 4B, the electrical power cable 20 is likewise fixed between the outer end 21 of guide 2 and the washing unit 6. The power cable 20 is routed in the longitudinal direction over a first longitudinal pulley 201 which is movable along the guide 2 in the longitudinal direction, and from said first longitudinal pulley 201 towards the connector 402 on the slider 4. From there the power cable 20 is routed from the connector 402 on the slider 4 in the lateral direction over a first lateral pulley 202 which is movable in the lateral direction, and from said first lateral pulley 202 towards a connector 619 on the washing unit 6, which connector 619 is connected to the electrical motors 603, 608. The longitudinal pulleys 101, 201 are mounted on a single pulley element 301 which is slidable along the guide 22, and the lateral pulleys 102, 202 are also mounted on a single pulley element 302.

A first tension wire 30 is fixed between the other outer end 22 of the first guide 2 and the first slider 4, and is routed from said outer end 22 over a second longitudinal pulley 302 on the pulley element 301, and from said second longitudinal pulley 302 to a third longitudinal pulley 303 which is fixed to the outer end 22, and from said third longitudinal pulley 303 to a fourth longitudinal pulley 304 which is fixed to the first outer end 21, and from said fourth longitudinal pulley 304 to said first slider 4. A second tension wire 31 is fixed between the second slider 5 and the washing unit 6, and is routed from said second slider 5, over a second lateral pulley 305 which is fixed to the pulley element 302, and from said second lateral pulley 305 to a third lateral pulley 306 which is fixed to said second slider 5, and from said third lateral pulley 306 to a fourth lateral pulley 307 which is fixed to said first slider 4, and from said fourth lateral pulley 307 to said washing unit 6.

In this manner the washing unit can move in both longitudinal and lateral directions to any location on the surface while the water hose 10 and power cable 20 remain tensioned by the tension cables 30, 31. The washing unit 6 may comprise a programmed controller, which may be programmed to control the motors 603, 608 automatically in accordance with a predetermined schedule to perform a washing cycle. The washing unit may also be provided with communication means arranged to receive instructions from an external controller to control the motors 603, 608 to perform a washing cycle. The invention has thus been described by means of preferred embodiments. It is to be understood, however, that this disclosure is merely illustrative. Various details of the structure and function were presented, but changes made therein, to the full extent extended by the general meaning of the terms in which the appended claims are expressed, are understood to be within the principle of the present invention. The description and drawings shall be used to interpret the claims. The claims should not be interpreted as meaning that the extent of the protection sought is to be understood as that defined by the strict, literal meaning of the wording used in the claims, the description and drawings being employed only for the purpose of resolving an ambiguity found in the claims. For the purpose of determining the extent of protection sought by the claims, due account shall be taken of any element which is equivalent to an element specified therein. An element is to be considered equivalent to an element specified in the claims at least if said element performs substantially the same function in substantially the same way to yield substantially the same result as the element specified in the claims.