USER-GUIDED SELF-PROPELLED CLEANING DEVICE

Abstract

A user-guided self-propelled cleaning device for cleaning a surface, having a frame which includes at least two tools and at least one drive, the at least two tools being rotatable on the surface by said at least one drive, wherein, when the self-propelled cleaning device is placed on the surface, each of the tools is inclined over at least one respective angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 with respect to the surface, and wherein the two tools are configured to rotate in mutually different directions in an operative state of the self-propelled cleaning device, thereby exerting a propulsive force on the frame, wherein said inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 is variable by manipulation, by a user, of a control element, to vary the propulsive force exerted on the frame.

Claims

1. A user-guided self-propelled cleaning device for cleaning a surface (S), having: a frame which includes at least two tools and at least one drive, for rotating the at least two tools on the surface (S), wherein, when the user-guided self-propelled cleaning device is placed on the surface (S), each of the tools is inclined over at least one respective angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 with respect to the surface (S), and wherein the two tools are configured to rotate in mutually different directions in an operative state of the self-propelled cleaning device, thereby exerting a propulsive force (P) on the frame, the device further comprises a control element for control of the user-guided self-propelled cleaning device by a user of the device, wherein said inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 variable by a manipulation of the control element by the user, to vary the propulsive force (P) exerted on the frame (11).

2. The user-guided self-propelled cleaning device according to claim 1, wherein said inclination angle Γ.sub.1, Γ.sub.2 is defined in or has a component when projected on an imaginary YZ plane of an imaginary XYZ axis system having an origin (O) in a central position with respect to the at least two tools (111, 112), an X-axis (X) of the XYZ axis system coinciding with a propulsion direction of the user-guided self-propelled cleaning device (1), a Z-axis (Z) of the XYZ axis system coinciding with a direction normal to the surface (S), and the Y-axis (Y) of the XYZ axis system pointing to the right of the frame (11) and completing the XYZ axis system.

3. The user-guided self-propelled cleaning device according to claim 1, having an articulated arrangement and a top part that includes at least one-handle, the top part being connected to the frame via said articulated arrangement, the top part preferably being pivotable in all angular directions with respect to the frame.

4. The user-guided self-propelled cleaning device according to claim 1, being a scrubber-drier having a water outlet at or near the rotatable tools and a suction strip arranged, when seen in a propulsion direction, behind the rotatable tools.

5. The user-guided self-propelled cleaning device according to claim 3, wherein the control element is defined by the top part and wherein the manipulation is defined by a backwards and/or forwards movement of the handle.

6. The user-guided self-propelled cleaning device according to claim 5, wherein a mechanical linkage system couples the movement of the handle and the movement of the tools.

7. The user-guided self-propelled cleaning device according to claim 5, wherein the handle of the top unit includes a handle position sensor configured for determining an angular position of the handle, wherein the frame includes a tool angle controller arranged in wired or wireless communication with the handle position sensor of the top unit, and wherein the tool angle controller is configured to alter the inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 of the tools based on the angular position of the handle.

8. The user-guided self-propelled cleaning device according to claim 3, wherein the inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 is between −1° and +1° when the handle is arranged substantially vertical, and/or wherein the inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 is between −1° and +1° when the handle is arranged substantially horizontally, and/or wherein the inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 is between +1° and +3° when the handle is arranged substantially transverse with respect to both the vertical and the horizontal orientation.

9. The user-guided self-propelled cleaning device according to claim 1, wherein the control element is defined by the handle, and wherein the manipulation is defined by a rotational movement of the handle.

10. The user-guided self-propelled cleaning device according to claim 1, wherein the control element is defined by a knob, switch, or button, said knob, switch or button being manipulable with a hand and/or foot of the user.

11. The user-guided self-propelled cleaning device according to claim 1, wherein the inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 of the rotatable tools can be varied in a stepless manner.

12. The user-guided self-propelled cleaning device according to claim 1, wherein propulsion of the cleaning device is solely effected by the propulsive force (P) resulting from the combination of inclination and counter-rotation of the tools.

13. The user-guided self-propelled cleaning device according to claim 1, wherein said inclination angle α.sub.1, α.sub.2 is defined in or has a component when projected on an imaginary XZ plane of an imaginary XYZ axis system having an origin (O) in a central position with respect to the at least two tools, an X-axis (X) of the XYZ axis system coinciding with a propulsion direction of the self-propelled cleaning device, a Z-axis (Z) of the XYZ axis system coinciding with a direction normal to the surface (S), and the Y-axis (Y) of the XYZ axis system pointing to the right of the frame (11) and completing the XYZ axis system.

14. The user-guided self-propelled cleaning device according to claim 1, wherein the drive is configured to rotate the tools with a variable rpm, to vary the propulsive force (P) exerted on the frame.

15. A method for cleaning a surface (S), wherein use is made of a user-guided self-propelled cleaning device according to any one of the claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0072] FIG. 1 very schematically illustrates an embodiment of the cleaning device according to the present disclosure from the below;

[0073] FIGS. 2A and 2B very schematically illustrate an embodiment of the cleaning device in respectively an isometric front view and a front view, in a first cleaning position;

[0074] FIGS. 3A and 3B very schematically illustrate the cleaning device of FIGS. 2A and 2B, in a second cleaning position;

[0075] FIGS. 4A and 4B very schematically illustrate the cleaning device of FIGS. 2A and 2B, in a third cleaning position;

[0076] FIGS. 5A and 5B very schematically illustrate the cleaning device in the same cleaning position as FIGS. 3A and 3B, but now from the side and from below;

[0077] FIGS. 6A-6D very schematically illustrate a further embodiment of the cleaning device in accordance with the present disclosure;

[0078] FIGS. 7A and 7B very schematically illustrate a yet further embodiment of the cleaning device in accordance with the present disclosure;

[0079] FIG. 8 very schematically illustrates a cleaning device having a deformable elastomeric element and a hinge; and

[0080] FIG. 9 very schematically illustrates a cleaning device having a deformable elastomeric element according to a second embodiment thereof.

DETAILED DESCRIPTION OF THE DRAWINGS

[0081] In the below description, all figures are described together, unless where reference is made to a specific figure. Some of the more important aspect of the disclosed cleaning device are thematically grouped to be explained in more detail.

Propulsion principle

[0082] Although the propulsion principle of self-propelled cleaning devices 1, 100 is in principle known in the field, it is here briefly described. With reference to FIGS. 1 and 3A, a self-propelled cleaning device 1 with two tools 111, 112 is shown. Each of the tools 111, 112 is driven by a drive 113, so that the tools 111, 112 are rotatable on a surface S to be cleaned. As is shown in FIG. 3A, each of the tools 111, 112 are inclined at an angle Γ.sub.1, Γ.sub.2 with respect to the horizontal orientation. As is shown in FIG. 1, each of the tools 111, 112 in operation rotate in mutual different directions, i.e. they counter-rotate. As a result of this inclination, a pressure on the tools 111, 112 is higher near the centre of the frame 11 than near the outer side of the frame 11. The combination of counter-rotation and inclination generates a propulsive force P. As a result of the propulsive force P the cleaning device 1, upon operation, moves forward and is self-propelled.

[0083] In principle, as will be explained in more detail below, the magnitude and direction of the propulsive force P depends on at least three factors: the pressure applied on the tools 111, 112, the inclination angles Γ.sub.1, Γ.sub.2 of the tools 111, 112, and the rpm of the tools 111, 112.

[0084] As will be clear from the above text and FIG. 1, it is possible to propel the cleaning device 1, 100 without any other propulsive means, such that propulsion of the cleaning device 1, 100 is effected solely by the propulsive force P resulting from the combination of inclination and counter-rotation of the tools 111, 112.

Vary Forward Speed by Modification of Tool Inclination Angle

[0085] One option to vary the forward speed of the cleaning device 1, 100 is to vary the inclination angles Γ.sub.1, Γ.sub.2 of the tools 111, 112. The tools 111, 112 may principally be inclined over two different angles Γ, α, and/or a combination of the two different angles Γ, α. In the shown figures, mainly visible in FIGS. 3B and 5A, the two different angles Γ, α are shown.

[0086] The inclination angle Γ, shown in FIG. 3B, is defined as an angle in or having a component when projected on an imaginary YZ plane of an imaginary XYZ axis system. The XYZ axis system has an origin O in a central position with respect to the tools 111, 112, an X-axis that coincides with a propulsion direction of the self-propelled cleaning device 1, 100, a Z-axis Z that coincides with a direction normal to the surface, and the Y-axis Y points to the right of the frame 11 and completes the XYZ axis system.

[0087] That is, the X axis points forwards out of the paper in FIG. 3B, the Z-axis Z corresponds to the vertical in FIG. 3B and the Y-axis Y points to the right in FIG. 3B.

[0088] The inclination angle α, shown in FIG. 5A, is defined as an angle in or having a component when projected on an imaginary XZ plane of same imaginary XYZ axis system. That is, the X axis points forwards in FIG. 5A, the Z-axis Z corresponds to the vertical in FIG. 5A and the Y-axis Y points out of the paper in FIG. 5A.

[0089] In the shown FIGS. 3B and 5A the tools 111, 112 have a positive inclination angle Γ.sub.1, Γ.sub.2 in the YZ plane and an inclination angle α.sub.1, α.sub.2 of zero in the XZ plane. In the FIGS. 2B and 4B the tools 111, 112 have an inclination angle Γ.sub.1, Γ.sub.2 of zero in the YZ plane and an inclination angle α.sub.1, α.sub.2 of zero in the XZ plane.

[0090] When the inclination angles Γ.sub.1, Γ.sub.2 are both zero, pressure is equally distributed over the tool area and no net propulsive force P is generated. When the inclination angles Γ.sub.1, Γ.sub.2 are positive, a positive propulsion force P is generated as described in the above. When the inclination angles Γ.sub.1, Γ.sub.2 are increased, the propulsion force P becomes larger. When the inclination angles Γ.sub.1, Γ.sub.2 are negative, pressure on the tools 111, 112 is higher near the outside of the frame 11 than near the centre of the frame 11 and a negative propulsion force P is generated.

Vary Forward Speed by Modification of Tool Rpm

[0091] Another option to vary the forward speed of the cleaning device 1, 100 is to vary the rotational speed of the tools 111, 112. Therefore, in the shown figures, the drive 113 is configured to rotate the tools 111, 112 with a variable rpm. When the tools 111, 112 rotate with a lower rpm, the propulsion force P decreases. When the tools 111, 112 rotate with a higher rpm, the propulsion force P increases. Also using this alternative option, a change in forward speed may be obtained.

Making a Turn

[0092] When the cleaning device 1 is of the hand-guided type, a turn may easily be made with the cleaning device by exerting a torque moment on the frame by turning handle 131 about the Z-axis.

[0093] Alternatively, a turn can be made automatically. This is possible when the cleaning device 1, 100 is of the hand-guided type, but this is mainly advantageous when the cleaning device 1, 100 is of the robotic or autonomous type. To make an automatic turn several options are possible as described in the below. The main goal to achieve is altering the direction of the propulsion force P. It should no longer align with the X-axis X but is should point to the right or to the left to make a right or a left turn.

[0094] One way to achieve this is by changing the rpm of one of the tools 111, 112 with respect to the other of the tools 111, 112. This will ensure that a turn is made in the direction of the fastest rotating tool 111, 112.

[0095] Another way to achieve this is by changing the inclination Γ.sub.1, Γ.sub.2 in the YZ plane of one of the tools 111, 112. When one of the tools 111, 112 has a higher inclination Γ.sub.1, Γ.sub.2 than the other tools 111, 112 the tool 111, 112 with a higher inclination Γ.sub.1, Γ.sub.2 pushes on the surface harder and the cleaning device 1, 100 is pulled in that direction.

[0096] Yet another way to achieve a turn is to change the inclination α.sub.1, α.sub.2 in the XZ plane of one of the tool 111, 112. This will alter the point on the surface S where the most pressure is applied by the tool 111, 112 and this will also tilt the propulsion force P.

Cleaning Task 1—Spot Cleaning

[0097] A first task that the cleaning device 1, 100 as presented herein can fulfil with great ease and with excellent success is spot cleaning—i.e. high intensity cleaning of a relatively small area of the surface to be cleaned. Preferably, to effect this spot cleaning, the tools 111, 112 are rotated with a relative high rpm and with a small inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 of e.g. between −1 degree and +1 degree, e.g. of zero degree. The cleaning device 1, 100 will then move slowly over the area to be spot-cleaned while the tools rotate at a high level, resulting in high intensity cleaning. It is noted that spot cleaning is less effective when the rpm is reduced to have the cleaning device move slower. For example, this setting can be obtained automatically, using sensors, or by having the handle 131 in a vertical position—as will be described in more detail in the below.

Cleaning Task 2—Cleaning in Corners

[0098] A second task that the cleaning device 1, 100 as presented herein can fulfil with great ease and with excellent success is cleaning in corners. For this, high precision is needed and it is in that respect beneficial when the cleaning device 1, 100 can be moved slowly. This can be obtained by having a small inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 of e.g. between −1 degree and +1 degree, e.g. of 0.5 degree. Possibly, when corners are cleaned also the rpm can be adjusted to a lower level, when cleaning with a higher intensity is not needed. For example, this setting can be obtained automatically, using sensors, or by having the handle 131 in a near vertical position—as will be described in more detail in the below.

Cleaning Task 3—Cleaning Below Objects

[0099] A third task that the cleaning device 1, 100 as presented herein can fulfil with great ease and with excellent success is cleaning below objects. For this, high precision is needed and it is in that respect beneficial when the cleaning device 1, 100 can be moved slowly. This can be obtained by having a small inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 of e.g. between −1 degree and +1 degree, e.g. of 0 degree or 0.5 degree. Possibly, when an area of the surface S below an object is cleaned also the rpm can be adjusted to a lower level, when cleaning with a higher intensity is not needed. In other cases, when the area is relatively dirty, cleaning at the normal rpm however may be desired. For example, this setting can be obtained automatically, using sensors, or by having the handle 131 in a horizontal position—as will be described in more detail in the below.

Cleaning Task 4—Cleaning a Large Unobstructed Area

[0100] A fourth task that the cleaning device 1, 100 as presented herein can fulfil with great ease and with excellent success is cleaning a large unobstructed and mildly dirty surface fast and properly. For this, high speed is preferred and it is beneficial in that respect when the speed of the cleaning device 1, 100 can be increased. This can be obtained by having a large inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 of e.g. between 1 degree and 3 degrees, e.g. of 1.5 degree or 2 degree. Depending on the dirtiness of the surface S and the speed with which it is cleaned, it may be desirable to also adjust the rpm of the tools 111, 112—to obtain the most satisfactory cleaning result. For example, this setting can be obtained automatically, using sensors, or by having the handle 131 in a tilted position—as will be described in more detail in the below.

Hand-Guided Cleaning Device

[0101] In the FIGS. 2, 3, 4 and 5 the cleaning device 1 is of the hand-guided type. The device 1 comprises a handle 131 that can be held by a user and that can be used to guide the device 1 along a surface S. The handle 131 is part of a top part 13, which top part 131 is connected to the frame 11 via an articulated arrangement 12. The articulated arrangement 12 allows the top part 13 to be pivoted in all angular direction with respect to the frame 11, so that the top part 13, including handle 131, can be moved backwards, forwards, to the left, to the right, and any combination thereof.

[0102] For example, the hand-guided cleaning device 1 may be a so-called scrubber-drier that has a water outlet 114 at or near the tools 111, 112 and a suction strip 115 arranged behind the tools 111, 112.

Robotic or Autonomous Cleaning Device

[0103] In FIGS. 6A-6D the cleaning device 100 is of the robotic type and does not comprise a handle nor an articulated arrangement. The inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 of the tools 111, 112 of the robotic cleaning device 100 are in the present embodiment controlled by tool angle controllers 116. The shown robotic cleaning device 100 comprises two tool angle controllers 116, one associated with each of the tools 111, 112 so that the tools 111, 112 can be individually controlled by the tool angle controllers 116. That is, the inclination angle Γ.sub.1, α.sub.1 of one of the tools 111 may be different compared to the inclination angle Γ.sub.2, α.sub.2 of the other of the tools 112.

[0104] As will be appreciated, the robotic cleaning device 100 is wheelless; propulsion of the robotic cleaning device 100 is solely effected by the propulsive force P generated by the tools 111, 112 in the manner described earlier with reference to FIG. 1. Therefore, in contrast to known robotic cleaning tools which do have wheels, the presented cleaning device 100 will not leave any marks on the cleaned surface S as there are no wheels driving over a mildly moist surface S.

[0105] For example, the autonomous cleaning device 100 may be a so-called scrubber-drier that has a water outlet 114 at or near the tools 111, 112 and a suction strip 115 arranged behind the tools 111, 112.

Changing the Inclination Angle of the Tools

[0106] There are many different ways to change the inclination of the tools 111, 112, several of which are described in a bit of detail here for illustrative purposes only. However, a person skilled in the art will be able to come up with many more solutions, each of which are deemed to be covered by the appended claims. It may be preferred that the inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 of the rotatable tools 111, 112 can be varied in a stepless manner.

[0107] When the cleaning device 100 is of the robotic type, it may e.g. comprise a tool angle controller 116 which is configured to alter the inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 of the tools 111, 112 as discussed in the above in relation to FIGS. 6A-6D. The tool angle controller 116 may e.g. receive input from a sensor that makes a scan of the environment or the surface S. Alternatively, the tool angle controller 116 may receive input from a pre-set program.

[0108] Also when the cleaning device 1 is of the hand-guided type, control of the inclination of the tools 111, 112 may be effected through manipulation of a control element 13, 131. For example, the device 1 may e.g. comprise a tool angle controller 116 which is configured to alter the inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 of the tools 111, 112, as is shown in FIGS. 7A and 7B. The tool angle controller 116 may e.g. receive input from a handle position sensor 132, and base the tool inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 on the angular position β of the handle 131 with respect to the Z-axis Z. For example, the handle position sensor 132 may determine a backwards and/or forwards movement of the handle 131, and vary the inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 of the tools 111, 112 based on the movement of the handle 131. In this embodiment the top part 13 is the control element, and the backwards and/or forwards movement of the top part 13 is the manipulation by the operator.

[0109] Another possibility is to mechanically link a movement of the handle 131 or top part 13 to the movement of the tools 111, 112, as is shown in FIGS. 2-4. When comparing FIGS. 2A and 3A, one can see that a movement of the handle 131 in the backwards direction results in a downwards movement of hinge 122 and, in turn, a deflection of levers 117. The deflection of levers 117 ultimately alters the inclination angle Γ.sub.1, Γ.sub.2, of the tools 111, 112. As shown, the inclination angles Γ.sub.1, Γ.sub.2, are only changed in the YZ plane and with the same amount, but variants of such a linkage system would also allow to individually address the tools 111, 112 and/or to change the inclination angle α.sub.1, α.sub.2 in the XZ plane.

[0110] Comparing now FIGS. 3A and 4A, one can see that when the handle 131 is moved further backwards, hinge 122 is moved back up again and, in turn, levers 117 are in the same neutral undeflected position as in FIG. 2A such that the inclination angle Γ.sub.1, Γ.sub.2 of the tools 111, 112 is again zero.

[0111] This movement of the tool inclination angle Γ.sub.1, Γ.sub.2 between two different inclinations when the handle 131 is moved between three different positions is made possible by the C-shaped guidance path along which the handle 131 moves in the mechanical linkage system 121. Also in this embodiment, top part 13 is the control element whereas the backwards and/or forwards movement of the handle 131 is the manipulation movement.

[0112] Other (non-shown) options to control the tool inclination are e.g. the rotational movement of the handle 131 which may corresponds to an alteration of the tool 111, 112 inclination angle Γ.sub.1, Γ.sub.2, e.g. through sensors and/or the manipulation of a switch, button or knob, e.g. with a hand or foot of the user, to alter the inclination angle Γ.sub.1, Γ.sub.2 of the tools 111, 112.

Movement of the Handle with Respect to the Frame

[0113] Turning now to FIG. 2A, in this embodiment an articulated arrangement 12 allows the handle 131 to be moved forwards and backwards with respect to the user through first hinge 122. First hinge 122 defines a rotation axis perpendicular to the direction of movement, to allow the handle 131 to be moved backwards and forwards. Second hinge 123 allows the handle 131 to be moved to the left and the right with respect to the user, about a rotation axis that is arranged parallel to the direction of movement. By implementing a first hinge 122 and a second hinge 123, the two hinges 122, 123 having rotation axes that are perpendicular to each other, the handle 131 can be rotated 360 degrees with respect to the frame.

[0114] Turning now to FIG. 8, shown is a cleaning device with a frame 11, an articulated arrangement 12 and a top part 13 including handle 131. The top part 13 is connected to the frame 11 via articulated arrangement 12. Articulated arrangement comprises a first hinge 122, and a deformable elastomeric element 123A. The first hinge 122 allows the handle 131 to be rotated about a first rotation axis. The rotation axis is perpendicular to the direction of movement so that, when seen from the perspective of the user, the handle 131 can be moved forwards and backwards about the first hinge 122. The elastomeric element 123A here has a non-constant cross-section—non-constant with regards to the shape as well as the size—with cut-outs 123B. The cut-outs locally weaken the elastomeric element 123A such that it becomes more flexible in one direction than in other directions. As such, the elastomeric element 123A is relatively rigid in the movement direction corresponding to the direction of movement whereas it is relatively flexible in the direction coinciding with the first rotation axis. As such, the elastomeric element 123A allows the handle 131 to be moved to the left and the right with respect to the user.

[0115] Turning now to FIG. 9, another embodiment of a user-guided cleaning device is shown. The user-guided cleaning device again has a frame 11, a top part 13 including handle 131 and an articulated arrangement 12 connecting the top part 13 and the frame 11. The articulated arrangement 12 is defined by a deformable elastomeric diabolo element 123C having a non-constant, rotationally symmetric shape. Although in this embodiment the cross section is circular in all (horizonal) planes, the diameter of the elastomeric element 123C is non-constant. This rotationally symmetric shape, in combination with the elastomeric material of which the diabolo element is made, has the effect that the handle 131 can be moved in any direction with respect to frame 11 with a relatively large accuracy—again resulting in a handle 131 that can be moved 360 degrees with respect to the direction normal to the surface to be cleaned.

[0116] These aspects of the present invention are alternatively defined by means of the below clauses:

CLAUSES

[0117] 1. A self-propelled cleaning device (1, 100) for cleaning a surface (S), having a frame (11) which includes at least two tools (111, 112) and at least one drive (113), the at least two tools (111, 112) being rotatable on the surface (S) by said at least one drive (113),  wherein, when the self-propelled cleaning device (1, 100) is placed on the surface (S), each of the tools (111, 112) is inclined over at least one respective angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 with respect to the surface (S), and  wherein the two tools (111, 112) are configured to rotate in mutually different directions in an operative state of the self-propelled cleaning device (1, 100), thereby exerting a propulsive force (P) on the frame (11),  characterised, in that said inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 is variable, to vary the propulsive force (P) exerted on the frame (11). [0118] 2. The self-propelled cleaning device according to clause 1, wherein said inclination angle Γ.sub.1, Γ.sub.2 is defined in or has a component when projected on an imaginary YZ plane of an imaginary XYZ axis system having an origin (O) in a central position with respect to the at least two tools (111, 112), an X-axis (X) of the XYZ axis system coinciding with a propulsion direction of the self-propelled cleaning device (1, 100), a Z-axis (Z) of the XYZ axis system coinciding with a direction normal to the surface (S), and the Y-axis (Y) of the XYZ axis system pointing to the right of the frame (11) and completing the XYZ axis system. [0119] 3. The self-propelled cleaning device according to any one of the preceding clauses, being a hand-guided self-propelled cleaning device (1) having an articulated arrangement (12) and a top part (13) that includes at least one handle (131), the top part (13) being connected to the frame (11) via said articulated arrangement (12), the top part (13) being pivotable in all angular directions with respect to the frame (11). [0120] 4. The self-propelled cleaning device according to any one of the preceding clauses, being a scrubber-drier (1, 100) having a water outlet (114) at or near the rotatable tools (111, 112) and a suction strip (115) arranged, when seen in a propulsion direction, behind the rotatable tools (111, 112). [0121] 5. The self-propelled cleaning device according to clause 3 or 4, wherein the inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 of said tools (111, 112) is variable by moving the handle (131) of the top part (13) backwards and/or forwards. [0122] 6. The self-propelled cleaning device according to clause 5, wherein a mechanical linkage system (121) couples the movement of the handle (131) and the movement of the tools (111, 112). [0123] 7. The self-propelled cleaning device according to clause 5, wherein the handle (131) of the top unit (13) includes a handle position sensor (132) configured for determining an angular position of the handle (131), wherein the frame (11) includes an tool angle controller (116) arranged in wired or wireless communication with the handle position sensor (132) of the top unit (13), and wherein the tool angle controller (116) is configured to alter the inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 of the tools (111, 112) based on the angular position of the handle (131). [0124] 8. The self-propelled cleaning device according to any one of the clauses 3-7, wherein the inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 is between −1° and +1° when the handle (131) is arranged substantially vertical, and/or wherein the inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 is between −1° and +1° when the handle (131) is arranged substantially horizontally, and/or wherein the inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 is between +1° and +3° when the handle (131) is arranged substantially transverse with respect to both the vertical and the horizontal orientation. [0125] 9. The self-propelled cleaning device according to any one of the preceding clauses, wherein the inclination angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 of the rotatable tools (111, 112) can be varied in a stepless manner. [0126] 10. The self-propelled cleaning device according to any one of the preceding clauses, wherein propulsion of the cleaning device (1, 100) is solely effected by the propulsive force (P) resulting from the combination of inclination and counter-rotation of the tools (111, 112). [0127] 11. The self-propelled cleaning device according to any one of the preceding clauses, wherein the frame (11) is wheelless. [0128] 12. The self-propelled cleaning device according to any one of the preceding clauses, wherein said inclination angle α.sub.1, α.sub.2 is defined in or has a component when projected on an imaginary XZ plane of an imaginary XYZ axis system having an origin (O) in a central position with respect to the at least two tools (111, 112), an X-axis (X) of the XYZ axis system coinciding with a propulsion direction of the self-propelled cleaning device, a Z-axis (Z) of the XYZ axis system coinciding with a direction normal to the surface (S), and the Y-axis (Y) of the XYZ axis system pointing to the right of the frame (11) and completing the XYZ axis system. [0129] 13. The self-propelled cleaning device according to any one of the preceding clauses, wherein the drive (113) is configured to rotate the tools (111, 112) with a variable rpm, to vary the propulsive force (P) exerted on the frame (11). [0130] 14. A self-propelled cleaning device (1, 100) for cleaning a surface (S), having a frame (11) which includes at least two tools (111, 112) and at least one drive (113), the at least two tools (111, 112) being rotatable on the surface (S) by said at least one drive (113),  wherein, when the self-propelled cleaning device (1, 100) is placed on the surface (S), each of the tools (111, 112) is inclined over at least one respective angle Γ.sub.1, Γ.sub.2, α.sub.1, α.sub.2 with respect to the surface (S), and  wherein the two tools (111, 112) are configured to rotate in mutually different directions in an operative state of the self-propelled cleaning device (1, 100), thereby exerting a propulsive force (P) on the frame (11),  characterised, in that the drive (113) is configured to rotate the tools (111, 112) with a variable rpm, to vary the propulsive force (P) exerted on the frame (11). [0131] 15. A method for cleaning a surface (S), wherein use is made of a self-propelled cleaning device (1, 100) according to any one of the clauses 1-13 and/or a self-propelled cleaning device (1, 100) according to clause 14.

LIST OF REFERENCE NUMERALS

[0132] 1 hand-guided self-propelled cleaning device [0133] 11 frame [0134] 111 rotatable tool [0135] 112 rotatable tool [0136] 113 drive [0137] 114 water outlet [0138] 115 suction strip [0139] 116 tool inclination angle controller [0140] 117 lever [0141] 12 articulated arrangement [0142] 121 mechanical linkage system [0143] 122 first hinge [0144] 123 second hinge [0145] 123A deformable elastomeric element [0146] 123B cut-outs [0147] 123C deformable elastomeric element [0148] 13 top part [0149] 131 handle [0150] 132 handle position sensor [0151] 100 robotic self-propelled cleaning device [0152] O origin of axis system [0153] P propulsive force [0154] S surface to be cleaned [0155] X X-axis [0156] Y Y-axis [0157] Z Z-axis [0158] α.sub.1 inclination angle first rotatable tool when projected on XZ plane [0159] α.sub.2 inclination angle second rotatable tool when projected on XZ plane [0160] β angle between Z-axis and handle [0161] Γ.sub.1 inclination angle first rotatable tool when projected on YZ plane [0162] Γ.sub.2 inclination angle second rotatable tool when projected on YZ plane