BACKGROUND OF THE INVENTION When manually cleaning with a brush, the brush may become very dirty which decreases the efficiency of the cleaning and increases the risk of scratching the surface to be cleaned with the dirt.

Brushes for high-pressure cleaners and in particular rotary brushes usually provide a flat surface of engagement to the object being cleaned. This geometry of engagement surface is not suited for cleaning of objects of complex geometrical shapes comprising for example holes, edges, grooves and channels. Examples of such objects are wooden furniture and automobiles, such as rims of automobiles.

For paddle wheel driven rotary brushes, the wheel houses are designed in a way to ensure that the fluid exit in the driving mechanism is placed away from the water entry.

The wheel must therefore rotate a fraction of a full rotation before the water may exit and hence, the water flow will be blocked if the rotation of the brush is blocked. In most cases this is undesired since the flowing water may assist in loosening a blocked brush.

When a high-pressure cleaner is equipped with a brush and used for cleaning of objects above the height of the grip, it leads to cleaning fluid flowing down the lance towards the operator. Eventually, the operator will get in direct contact with the cleaning fluid, which is highly undesired.

OBJECTS OF THE INVENTION

It is an object of the invention to provide a brush for improved cleaning of objects, primarily of complex geometrical shapes, such as holes and/or edges and/or grooves and/or channels, e. g. objects like wooden furniture and rims of automobiles.

In another aspect of the invention, it is a further object of the invention to provide a brush, which is self-cleaning.

In a further aspect of the invention, it is an object to provide a brush with a rotating brush housing, which is less prone to blocking of waterflow.

In yet another aspect of the invention, the object is to provide a back flow stopper to prevent fluid dispersed out of the brush from flowing down the transportation system of the pressurised fluid or at least to reduce the amount of water flowing along the outer surface of the transportation system, hence providing a more tidy operation of the device.

DISCLOSURE OF THE INVENTION The above and more objects are individually or in combination realised by the invention as described in the figures, the preferred embodiments and the claims.

In a first main aspect, the present invention provides a brush unit comprising - a brush housing - a number of brush members attached to said brush housing - a number of holes in said brush housing for controlled release of fluid - a means for releasable attachment to a transportation system for pressurised fluid, said means preferably comprising screw action, hooks and loops, press studs, friction connection or bayonet clutch.

By providing the brush with holes for controlled release of the high-pressure fluid, this fluid may clean the brush during the cleaning action. This will reduce the expected decrease in efficiency due to dirt building up in the brush as well as decrease the risk of scratching the surface to be cleaned with the dirt from the cleaning, as this dirt is washed away.

In a second main aspect, the invention provides a device for high-pressure cleaning comprising - a motor-pump unit for supplying of pressurised fluid - a transportation system for pressurised fluid connected to the high- pressure side of said motor-pump unit - a brush unit according to the first aspect of the invention, said brush unit being connected releasably to said transportation system.

These and further aspects within the inventive concept are discussed further in the following and exemplified in a number of non-limiting, preferred embodiments with reference to the figures.

The preferred pressurised fluid or cleaning fluid is substantially water. However, a number of additives may be added to enhance the cleaning action. Such additives are preferably selected from the group of detergents, pH-regulators, surfactants, lubricants, complex formation agents, mechanical grinding agents and chemo- mechanical polishing agents. More than one additive may be used simultaneously when this is desired.

The elements of the brush unit may individually be made from a rigid material, preferably a metal like stainless steel or aluminium, or a plastic-based material.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a device for high-pressure cleaning.

Fig. 2 shows a brush unit.

Fig. 3 shows a number of different geometrical shapes of the engagement surface of the brush members.

Fig. 4 shows brushes where the outmost part of the brush housing is detachable.

Fig. 5 shows sketch of brushes with holes placed in zones.

Fig. 6 shows a section of a brush housing.

Fig. 7 shows various steps of the action of a hole-sizing means on a brush unit.

Fig. 8 shows an embodiment of a hole-sizing means.

Fig. 9 shows a brush unit with a built-in high-pressure nozzle placed in the front of the brush unit.

Fig. 10 shows preferred embodiments of placement of brush elements into a brush member.

Fig. 11 shows preferred embodiments of placement of brush members on a brush housing.

Fig. 12 shows various preferred embodiments of back flow stoppers on a brush unit.

Fig. 13 shows various preferred embodiments of back flow stoppers on a lance.

Fig. 14 shows a preferred embodiment of a back flow stopper of a rotary brush unit.

Fig. 15 shows a brush unit with a rotatable brush housing separated into sections.

Fig. 16 shows a preferred embodiment of a gear.

Fig. 17 shows a preferred embodiment of a gear in another perspective.

Fig. 18 shows various types of hydraulic driving means.

Table of identification Number Description 1 Device for high-pressure cleaning 2 Motor-pump unit 3 Transportation system for pressurised fluid 4 Brush unit 5 Connection between transportation system and brush unit 6 High-pressure hose 7 Lance 10 Brush housing 11 Brush member 12 Hole for controlled release of fluid 13 Rounded and optionally detachable end of brush 14 Means for releasable attachment a Opening angle of conical engagement surface 20 Substantially conical engagement surface of brush 21 Possible rounding of end of brush 22 Diameter of brush with substantially cylindrical engagement surface 23 Substantially cylindrical engagement surface of brush 24 Innermost diameter of brush with substantially frustum of a cone engagement surface 25 Outermost diameter of brush with substantially frustum of a cone engagement surface 26 Substantially frustum of a cone engagement surface of brush Number Description 27 Diameter of brush with substantially segment of a sphere engagement surface 28 Substantially segment of a sphere engagement surface of brush 29 Substantially paraboloid engagement surface of brush 30 Substantially segment of an ellipsoid engagement surface of brush 31 Engagement surface 32 Rounded end of brush housing 33 A part of an optionally releasable end of the brush housing that is not rounded 34 Optionally means for detachable connection of an end of the brush housing 40 Indication of change of zone 41 Holes of different densities 42 Holes of different sizes 43 Holes of different geometrical shapes 50 Cross section view of brush housing 51 Inside of brush housing 52 Hole with controlled release direction of fluid 53 Guiding edges 60 Holes in brush housing 61 Mean for controlling of hole-sizing means 62 Hole-sizing means covering a fraction of the holes 63 Open section of hole-sizing means 64 Closed section of hole-sizing means 65 Hole-sizing means 70 Brush element 71 Hole within brush member 72 Top view of brush housing 73 Indications of preferred places for starting the detachable end 74 Nozzle 75 Detachable end of brush housing with nozzle p Angle from brush housing to brush member 76 Back flow stopper placed near the back of the brush unit 77 Back flow stopper placed in relation to the means for releasable attachment 80 Large plane back flow stopper placed on the lance 81 Small plane back flow stopper placed on the lance Number Description 82 Cup-shaped back flow stopper 83 Collar-shaped back flow stopper 84 Back flow stopper placed on the brush housing 90 Brush base 91 Gear unit 93 Drive wheel of the brush housing 94 Turbine wheel 95 High-pressure nozzle 100 High-pressure nozzle 101 Indicator of fluid flow 102 Paddle wheel 103 Indicator of direction of rotation 104 Turbine wheel based on paddle wheels 105 Turbine wheel based on propeller blades 106 Turbine blade 107 High-pressure nozzle. Fluid flowing downwards 108 Indicator of direction of rotation 109 Another type of turbine wheel 110 Turbine blade 111 Fluid guide

DESCRIPTION OF THE DRAWINGS In Fig. 1 a schematic sketch of a device 1 for high-pressure cleaning is shown. The device in Fig. 1 comprises a motor-pump unit 2, a transportation system 3, a brush unit 4, and a connection 5 between the transportation system 3 and the brush unit 4. The transportation system comprises a high-pressure hose 6 and a lance 7 including a grip.

In Fig. 2 a preferred embodiment of a brush unit is shown. The brush unit comprises a brush housing 10 whereon a number of brush members 11 are fastened. Furthermore, the brush housing comprises a number of holes 12 for controlled release of the fluid, optionally pressurised fluid. In the end facing the fluid transportation system, a means 14 for releasable attachment of the brush unit to the transportation system is

observed. The brush is optionally equipped with a nozzle, optionally a high-pressure nozzle (not seen in Fig. 2). The controlled release of the fluid may involve release of a substantially pressureless fluid, release of a low-pressure fluid or release of a high- pressure fluid. Particularly, if the brush is a rotatable brush, it may be advantageous to release the fluid substantially pressureless.

In the end of the brush facing away from the transportation system, this preferred embodiment is equipped with a rounded and optionally detachable part 13 of the brush housing 10. This part may be changed to provide a tip, which is optimised for a particular application. Hence, in many cases it is not necessary to have a special brush unit for each application but only a special tip. Furthermore, the tip is typically the part of the brush unit experiencing the toughest wear and by making the tip detachable it is possible to recycle the bulk of the brush unit and only replace the tip.

Replacement tips or other replacement parts may be provided separately or in a kit together with e. g. a brush unit.

The tip may be made from another material than the brush housing, particularly to increase the wearability or to reduce the risk of introducing scratches in the object to be cleaned. Preferably, the tip may comprise a substantially harder material than the main component of the brush housing to increase wearability and/or to prevent dirt from becoming indented into tip and hence prevent scratching by indented dirt.

Alternatively, the tip may comprise a substantially softer material such as e. g. a rubber-based or relatively soft plastic-based material to reduce the risk of introduction of scratches from the tip itself.

The tip may be rounded, preferably to form substantially a segment of a sphere, segment of a paraboloid or segment of an ellipsoid. Rounding of the tip decreases the chance of the brush tip getting caught in a surface feature, hence enhancing the cleaning action. The rounding of the tip may take place by either shaping the brush housing or by adjusting the length or direction of the brush members near the tip, thereby forming a rounded engagement surface of the brush members or a combination of the two methods. The detachable connection means is a fast and secure connection means like for example screw action, hooks and loops, press studs, friction connection or bayonet clutch.

A brush unit may be distributed individually or as part of a kit. Such a kit may for example further comprise a motor-pump unit, a transportation system for pressurised fluid and/or a replacement part, such as a replacement tip, and/or an enhancement part providing for further application options, such as a tip or brush housing having brush members with different stiffness.

In Fig. 3 a number of preferred embodiments of geometrical shapes of engagement surfaces of a brush unit is shown. The engagement surfaces of a brush consist of a number of ends of brush members. However, to increase clarity the individual brush members are not shown. Instead, the shown geometrical shapes should be understood as the practical engagement surface realised by the brush members placed onto the brush housing which may or may not take the same shape as the engagement surface dependent on if all brush members have the same average brush element length. All brushes are equipped with means 14 for connection to the fluid transportation system, said connection preferably being releasable.

Fig. 3A shows a brush with a substantially conical engagement surface 20. The advantage of the conical shape is that when cleaning with the side of the brush on a flat surface, the hands of the operator will not get into contact with the surface due to the opening angle a being greater than 0°. The opening angle may vary within a wide range with the low angels e. g. 10° < a <45°, being particularly efficient in cleaning objects with grooves, etc. Higher opening angles e. g. 45° < a < 120° are particularly good for cleaning of multi-edged objects.

Fig. 3B shows a brush with a substantially cylindrical engagement surface 23. Such a brush works best on surfaces which are not too big. The brush should have a diameter 22 in the order of between 1 cm to 20 cm, preferably 3 cm to 10 cm.

Fig. 3C shows a brush with a substantially frustum of a cone engagement surface 26.

This geometry is also advantageous for cleaning flat surfaces and edges with a diameter between the innermost diameter 24 and the outermost diameter of the brush.

The diameter of the innermost diameter 24 should be in the order of between 2 cm to 20 cm, preferably 5 cm to 15 cm to allow for a wide span of application. To realise the advantage of the shape, the outermost 25 diameter should be smaller than that of the innermost diameter 24.

Fig. 3D, E and F respectively show brushes with engagement surfaces substantially of a segment of a sphere 28, segment of an ellipsoid 30 and paraboloid 29 engagement surface. Such brushes may for example be particularly useful for cleaning of wavy surfaces like for example certain types of ceiling and for cleaning of gutters. The diameter 27 of a brush of substantially a segment of a sphere engagement surface should preferably be between 0.5 cm to 30 cm, more preferably 1 cm to 15 cm and even more preferably 2 cm to 10 cm.

The intervals of dimensions mentioned with regard to the embodiments shown in Fig.

3 should be considered as guides only. For some applications, brushes with considerably greater or smaller dimensions may be advantageous.

The tips of particularly the brushes shown in Fig. 3A, B and C may be rounded 21 and/or optionally equipped with a detachable end of the brush housing. In Fig. 4 an example of such a detachable end 13 is shown. 31 indicates the engagement surface of the brush. The means 34 for detachable connection of the end to the rest of the brush may be placed primarily on the tip as shown in Fig. 4B, or on rest of the brush unit as shown in Fig. 4C.

The detachable tip 13 in Fig. 4B comprises both the rounded tip 32 and a detachable part of the brush housing not rounded 33, whereas the tip in Fig. 4C mainly consists of the rounded tip 13.

In Fig. 5 examples of the holes for fluid release is discussed. The fluid released from the holes may serve several purposes including cleaning of the brush members and/or optionally enhancing the cleaning action, e. g. by high-pressure cleaning, by washing away the dirt loosened by the brush unit or by a combination of these. The balance between the various types of cleaning actions of the fluid depends to a great extent on the type, shape and size of the holes of the brush housing, since the greater the area of holes, the lower the pressure of the released fluid. The holes may take a wide range of sizes, densities and shapes comprising substantially circular, polygonal, triangular, square, rectangular and elliptic, however, the preferred shape being circular. In a preferred embodiment, the holes are designed to realise a substantially pressureless release of the fluid. This embodiment may for example be advantageous for some brushes with a rotatable brush housing.

The variation of shape, area and density of holes may vary over the surface of the brush, preferably the variation follows a number of zones 40. The number of zones typically varies between 1 to 6. In Fig. 5A the density 41 of holes vary between the zones. In Fig. 5B the size 42 of the holes varies and in Fig. 5C the geometrical shape 43 varies. Particularly, one or more of the zones may not have any holes as e. g. zone 44.

Since one of the purposes of the fluid may be to clean the brush members, one way of directing the fluid released from a hole 52 towards a brush member 11 is shown in Fig.

6. Here a cross section of a brush housing is seen. The fluid accesses the hole 52 from the inside of the brush housing 51 into the directed hole 52 by the guiding edges 53, whereby the released fluid will be directed towards the brush member 11 to enhance cleaning of that brush member. Other methods for releasing dedicated for cleaning of specific brush members are also feasible. See e. g. Figures 10G and 10G' where fluid is released within a brush member.

Fig. 7 illustrates an embodiment of a hole-sizing means. As discussed above, the pressure of the released fluid heavily depends on the area of the holes. Hence by changing the area of the holes the pressure of the released fluid may be adjusted. In Fig. 7 A the holes 60 are not effected by the hole-sizing means and may for example be released substantially pressureless, whereas in Fig. 7B and C the holes 60 are gradually covered by the hole-sizing means 62. The position of the hole-sizing means may be controlled from a position on the device for high-pressure cleaning, however, in the embodiment shown here, it is controlled by the means 61 for controlling of hole- sizing means by mechanical movement.

In Fig. 8 one embodiment of a hole-sizing means 65 is shown. In Fig. 8A the brush housing is seen with the holes 60. In Fig. 8B the hole-sizing means 65 to be inserted into the brush housing (Fig 8A) is shown. This hole-sizing means 65 comprises open 63 and closed 64 zones in the length direction of the brush unit. The position of the hole-sizing means 65 is controlled by a mean 61 for controlling of the hole-sizing means.

The advantage of using a hole-sizing means for changing the pressure of the released water is that it is faster to use the hole-sizing means than to change the brush unit. In an embodiment, a brush with a hole-sizing means further comprises a nozzle 74,

optionally a high-pressure nozzle such as in Fig. 9. Such nozzle may be placed in or near the tip of the brush 75. The nozzle 74 will not be active if the area of the holes is large. However, if the area of the holes is changed by a hole-sizing means the high- pressure nozzle will start to act. This is particularly useful if the hole-sizing means is controllable from the lance.

In one preferred embodiment, a nozzle 74, optionally a high-pressure nozzle is placed in a detachable end 75 of a brush housing. The detachable end 75 may be detachable in either position marked by 73. Placing a nozzle into the tip of the brush unit does not require the presence of a hole-sizing means.

Fig. 10 shows a number of preferred arrangements of brush elements 70 into brush members 11.

Fig. 10A shows a brush member having brush elements of substantially same length and placed substantially parallel. In Fig. 10A'the element is seen from the direction orthogonal to the brush housing.

Fig. 10B shows a brush member having brush elements of substantially same length and placed in any direction away form the surface of the brush housing. In Fig. 10B' the element is seen from the direction orthogonal to the brush housing.

Fig. 10C shows a brush member having brush elements of substantially same length and placed at a minimum angle away form the surface of the brush housing. In Fig.

10C'the element is seen from the direction orthogonal to the brush housing.

Fig. 10D shows a brush member having brush elements of substantially same length and placed at fixed angle away form the surface of the brush housing, thus forming a collar-shaped brush member. In Fig. 10D'the element is seen from the direction orthogonal to the brush housing.

Fig. 10E shows a brush member having brush elements of substantially same length and placed at two fixed angles away from the surface of the brush housing, thus forming a double collar-shaped brush member. In Fig. 10E'the element is seen from the direction orthogonal to the brush housing. In Fig 10C and D brush members with one and two fixed angles are shown, however, a larger number of fixed angles are also feasible like for example 3,4, 5 or 6 fixed angles.

Fig. 10F shows a brush member having brush elements with a plurality of lengths and placed substantially parallel. Fig. 10F'shows a brush member having brush elements with a plurality of lengths and placed in any direction away from the brush housing but with an engagement surface substantially parallel to the brush housing. The length of

a brush element as well as the thickness influences the properties of the brush element as well as the brush member. Examples of influenced properties are stiffness and strength. The distance between the individual brush elements within an individual brush member may also influence the properties of that brush member, as closely spaced brush elements are more likely to support each other during use. Hence the brush elements in a brush member with closely spaced brush element may appear stiffer than an equivalent brush element in a more openly spaced brush element.

Fig. 10G and G'correspond to Fig. 10A and B, respectively, with the addition that a hole 71 for release of fluid is placed within the brush member.

In general, it may be advantageous to use brush units with brush elements not extending orthogonal to the surface, since this may provide a better angle of engagement of the individual brush elements to the surface to be cleaned. This is particularly important, when the brush is a rotatable brush.

In Fig. 11 is shown a number of preferred arrangements of brush members 11 onto brush housings seen as cross sections 50.

In Fig. 11A a brush member is placed substantially orthogonal to the surface of the brush housing.

In Fig. 11 B a brush member is placed at an angle ß off the orthogonal direction to the surface of the brush housing. The angle ß is substantially between 10° to 60°, preferably 15° to 45°.

In Fig. 11 C the number of brush elements shown as the width of the brush member is substantially constantly the same for all brush members. Furthermore, the mean lengths of the brush elements are substantially the same in all brush members.

In Fig. 11D the number of brush elements shown as the width of the brush member varies significantly between the individual brush members of a brush unit.

In Fig. 11 E the mean lengths of the brush elements shown as the height of the brush members vary significantly between the individual brush members on a brush housing.

In Fig. 11 F and E a top view of a brush housing 72 is shown. The brush members may be arranged with substantially the same density as seen in Fig. 11F or with a significant variation of the density as seen in Fig. 11G.

If one or more of the properties of the brush members 11 varies significantly, the brush members with substantially equivalent properties are preferably arranged in the same zone.

In Fig. 12,13 and 14 a number of preferred embodiments of back flow stoppers are shown. A back flow stopper is particularly advantageous when using the cleaner at a higher position than the holding area of the transportation system. In this situation, the transportation system will be oriented at an angle sloping downward towards the operator. Cleaning fluid is hence likely to flow along the transportation system towards the operator unless a back flow stopper is provided.

The back flow stopper works by providing a means, which is typically in the shape of an edge, optionally a relatively sharp edge, that will force the major part of the fluid flowing towards the operator along the brush unit or transportation system to drip off the edge, thereby preventing the fluid from reaching the operator or at least reduce the amount of fluid reaching the operator. The edge may for example be formed by a stiff member such as e. g. a solid sheet or bulk piece of material or a flexible member optionally comprising a number of smaller members such as small strips, brush elements or brush members.

In Fig. 12A the back flow stopper 76 is placed by the end of the brush unit facing towards the transportation system of the high-pressure fluid. In Fig. 12B the back flow stopper 77 is placed in relation to the means for releasable attachment of the brush unit to the transportation system.

In Fig. 13 the back flow stoppers are placed on the lances 7. In Fig. 13A the back flow stopper 80 is a large plane. In Fig. 13B the back flow stopper 81 is a smaller plane.

This plane has preferably a smaller diameter than the brush. This reduces the chance of scratching the object to be cleaned with the back flow stopper. In Fig. 13C the back flow stopper 82 is shaped like a cup with the opening away from the brush unit. In Fig.

13D the back flow stopper 83 is shaped like a collar open away from the brush unit.

In Fig. 14 the back flow stopper is seen as a dark edge extending beyond the rest of the brush base.

In Fig. 15 a rotatable brush is shown when separated into the individual sections. The means 14 for releasable connection of the brush unit to the transportation system may be of a fast and secure connection like for example screw action, hooks and loops, press studs or bayonet clutch. The gear unit 91 is preferably placed within the brush base 90, but other positions e. g. as a separate part may also be feasible. The brush

housing 10 is equipped with brush members 11, holes 12 and optionally a rounded and/or detachable end of the brush housing 13.

The gear unit 91 shown here is a basic unit which reduces the rotational speed of a drive wheel for the brush housing relative to the rotational speed of a turbine wheel by a fixed factor of between 2 to 100 or 10 to 50. However, the gear unit may also increase the rotational speed of a turbine wheel by a fixed factor. In this case, the factor should be between 1.5 to 10. If desired, it is also possible to provide the gear unit with more than one fixed ratio, i. e. more than one gearing factor. In a specific case, the gear may provide a continuously changeable gearing factor. Another feature, which may be built into the gearing, is a neutral gear, i. e. a gear position, where rotation of the turbine wheel is not transferred to the drive wheel of the brush housing.

A special feature could also be an option of reversing the rotation of the brush housing relative to the brush housing. The reverse as well as the neutral gear may for example be useful if the brush unit is stuck. If a gear with more than one gearing factor is utilised, the gearing may for example be controllable from a place on the device for high-pressure cleaning, preferably on the lance.

In Fig. 16 a brush base with a turbine wheel 94 driven hydraulically by the pressurised fluid via the high-pressure nozzle 95 is shown. A preferred embodiment of the gear unit 91 is seen in details. In the front of the gear pointing away from the means for releasable attachment 14, a drive wheel 93 for brush housing is observed. When the brush housing is connected to the brush base and the gear, drive wheel 93 will communicate with the brush housing to transfer the rotational action. The brush housing should be equipped with a corresponding means for communication to receive the action from drive wheel 93. Here, the drive wheel 93 will communicate by direct interaction between the teeth of the drive wheel 93 and corresponding teeth of the brush housing, but other means for communication is also feasible such as e. g. a frictional connection. Thereby a rotation of the brush housing relative to the brush base may be realised upon rotation of the turbine wheel 94, which again may be rotated by the action of fluid from the high-pressure cleaner via the high-pressure nozzle 95. The drive wheel 93 as well as other parts of the gear may have other designs and may be placed in other parts in or near the brush without departing from the inventive idea disclosed here. Particularly, the drive wheel 93 may be placed near the brush base.

Fig. 17 also shows a brush base, this time with the gear unit 91 assembled. The turbine wheel 94 and the drive wheel 93 of the brush housing are clearly visible.

In Fig. 18 a number of hydraulic driving means are shown. Fig. 18 A shows a turbine wheel 104 based on paddle wheels 102. The fluid is introduced from the high-pressure nozzle 100 along the direction of the arrow 101. This leads to a rotation of the turbine wheel. The paddle wheel is typically placed near a fluid guide 111 to realise a sufficiently high transfer of energy from the pressurised fluid to the rotation. In Fig. 18B and C turbine wheels 105 and 109 based on propeller-like blades 106 and 110 are shown. The fluid is introduced from a direction substantially orthogonal to the plane of the paper that is substantially parallel to the rotational direction of the brush unit and off the axis of the rotation. In Fig. 18D and E the same configuration is shown with the fluid being introduced substantially on the rotational axis of the turbine wheel.

The embodiments shown in Fig. 18B, C, D and E are the preferred embodiments, since this arrangement provides a better transmission of the power of the high- pressure liquid to the turbine wheel and gives the opportunity of having a continued flow of fluid even if the rotation of the brush housing is blocked. Furthermore, this type of configuration opens up for much more compact design of the brush units.