SE2150458A1 - Cutting arrangement and lawnmower - Google Patents

Abstract

A cutting arrangement (2) is disclosed configured to be attached to a lawnmower (1) to cut vegetation. The cutting arrangement (2) comprises a cutting guard (3), and a cutting unit (4) configured to rotate such that one or more radially outer portions (4’) of the cutting unit (4) orbits in a circular path (C) inside the cutting guard (3). The cutting guard (3) comprises a front section (5) and a rear section (6) together enclosing a portion of the cutting unit (4). A first radial distance (r1) from the circular path (C) to an inner surface (5’) of the front section (5) of the cutting guard (3) is greater than a second radial distance (r2) from the circular path (C) to an inner surface (6’) of the rear section (6) of the cutting guard (3). The present disclosure further relates to a lawnmower (1) comprising a cutting arrangement (2).

Description

TECHNICAL FIELD The present disclosure relates to a cutting arrangement configured to be attached to a lawnmower to cut vegetation. The present disclosure further relates to a lawnmower comprising a cutting arrangement.

BACKGROUND A lawnmower is an apparatus capable of cutting grass of a lawn. Various types of lawnmowers exist on today's market. Examples are walk-behind mowers and self-propelled robotic lawnmowers. A walk-behind mower is a lawnmower usually comprising an elongated handle allowing a user to push, and/or to guide, the lawnmower. Some walk-behind mowers comprise a propulsion arrangement configured to drive one or more wheels of the lawnmower. Walk-behind mowers lacking a propulsion arrangement are sometimes referred to as “push mowers”. Some lawnmowers comprise a power unit in the form of an electric motor configured to rotate the cutting unit and some lawnmowers comprise a power unit in the form of a combustion engine configured to rotate the cutting unit.

A self-propelled robotic lawnmower is a mower capable of cutting grass in areas in an autonomous manner. Some robotic lawnmowers require a user to set up a border wire around a lawn that defines the area to be mowed. Such robotic lawnmowers use a sensor to locate the wire and thereby the boundary of the area to be trimmed. ln addition to the wire, robotic lawnmowers may also comprise other types of positioning units and sensors, for example sensors for detecting an event, such as a collision with an object within the area. The robotic lawnmower may move in a systematic and/or random pattern to ensure that the area is completely cut. A robotic lawnmower usually comprises one or more batteries and one or more electrically driven cutting units being powered by the one or more batteries. ln some cases, the robotic lawnmower uses the wire to locate a recharging dock used to recharge the one or more batteries. Generally, robotic lawnmowers operate unattended within the area in which they operate. Examples of such areas are lawns, gardens, parks, sports fields, golf courts and the like.

Lawnmowers of various type are associated with some mutual problems. One such problem is energy consumption of the lawnmower. That is, cutting grass usually requires a lot of energy. Due to environmental concerns, it is a great advantage if lawnmowers and associated arrangements and systems can be arranged to operate in an energy efficient manner. Moreover, after a certain time of operation, an energy storage unit of a lawnmower, 2 such as a battery or fuel tank, has to be charged or refilled. Thus, by reducing the energy consumption of the lawnmower, more available operational time of the lawnmower can be obtained given a certain energy storing capacity of the energy storage unit of the lawnmower. Furthermore, a more cost-efficient lawnmower can be provided because the consumption of fuel or electricity incurs costs.

Another such problem is the cutting result, which can be subdivided into visual cutting result and uniformity of cutting. The visual cutting result can be defined as the visual cutting result determined by a person viewing a mowed lawn. The uniformity of the cutting can be defined as uniformity of a length of the grass of a mowed lawn, i.e. if straws of the grass in a lawn are cut to a uniform length. Most lawnmowers comprise a cutting arrangement comprising a cutting guard and a cutting unit, wherein the cutting unit is configured to rotate inside the cutting guard during operation. Cutting guards are used to increase safety during operation of a lawnmower and during handling of the lawnmower.

A common problem for lawnmowers is that traces may be formed in the lawn having shorter or longer length of grass. Such traces significantly reduce the visual appearance of the lawn. One aspect that reduces the cutting result is that grass tend to bend when a cutting arrangement is moved over the lawn. The grass may then become straighter again which causes an uneven cutting result and impair the visual appearance of the lawn.

One way to improve the cutting result is to ensure that the grass is lifted towards the cutting unit when cutting unit is moved over the lawn. This can be performed by arranging the cutting unit with one or more surfaces being angled relative to a rotation plane of the cutting unit. ln this manner, a negative pressure can be generated inside the cutting guard which lifts grass towards the cutting unit. This method is highly efficient when it comes to cutting result and visual appearance of a lawn after cutting. However, this method is also highly energy consuming. This is because the energy needed for creating the negative pressure inside the cutting guard increases the rotational resistance of the cutting unit and hence the energy consumption of the cutting arrangement. Another aspect is that the attack angle of the angled surfaces not only generates a negative pressure inside the cutting guard but also some air flow in unwanted directions which adds to the increase in rotational resistance of the cutting unit and hence the energy consumption of the cutting arrangement.

Another problem associated with lawnmowers is decomposition of grass clippings. That is, grass cut by the lawnmower takes time to decompose, and such grass clippings may have a negative impact on the visual cutting result because grass clippings may accumulate to form 3 strings or clumps on the lawn. Apart from having a negative impact on the visual cutting result, accumulated gras clippings may disturb and annoy users of the lawn.

Furthermore, generally, on today's consumer market, it is an advantage if products, such as lawnmowers and associated components, systems, and arrangements, have conditions and/or characteristics suitable for being manufactured and assembled in a cost-efficient mannef.

SUMMARY lt is an object of the present invention to overcome, or at least alleviate, at least some of the above-mentioned problems and drawbacks.

According to a first aspect of the invention, the object is achieved by a cutting arrangement configured to be attached to a lawnmower to cut vegetation. The cutting arrangement is configured to be attached to the lawnmower such that a fon/vard direction of the cutting arrangement coincides with a fonNard direction of the lawnmower. The cutting arrangement comprises a cutting guard and a cutting unit configured to rotate such that one or more radially outer portions of the cutting unit orbits in a circular path inside the cutting guard. The cutting guard comprises a front section and a rear section, seen relative to the forward direction of the cutting arrangement. The front section and the rear section together enclose a portion of the cutting unit. A first radial distance from the circular path to an inner surface of the front section of the cutting guard is greater than a second radial distance from the circular path to an inner surface of the rear section of the cutting guard.

Since the first radial distance from the circular path to the inner surface of the front section of the cutting guard is greater than the second radial distance, a cutting arrangement is provided having conditions for cutting grass in an energy efficient manner while having conditions for obtaining an improved cutting result. The cutting result can be improved because grass is allowed to raise to an upright straight position by its own stiffness after having been bent by the front section of the cutting guard during movement of the cutting guard in the fonNard direction over a lawn.

That is, studies have shown that the bending of the grass caused by the front section of a cutting guard impairs the cutting result because a large proportion of the grass do not have time to raise to an upright straight position by its own stiffness to reach the cutting unit. However, due to the greater distance from the front section of the cutting guard to radially outer portions of the cutting unit, at least a larger proportion of the grass will have time to 4 raise to an upright straight position by its own stiffness after having been bent by the front section of the cutting guard. Thereby, conditions are provided for an improved cutting result. l\/loreover, the need for forming a large negative pressure inside the cutting guard is circumvented, or at least reduced, which provides conditions for operating the cutting arrangement in an energy efficient manner. ln addition, the greater distance from the front section of the cutting guard to the circular path can reduce the negative pressure inside the cutting guard which in turn can reduce the rotational resistance of the cutting unit and hence the energy consumption of the cutting unit.

Thus, due to the features of the cutting arrangement, the energy consumption of a lawnmower comprising the cutting arrangement can be lowered and the cutting result can be improved. ln addition, the cutting arrangement provides conditions for increasing available operational time of a lawnmower comprising the cutting arrangement before an energy storing unit of the lawnmower has to be charged or refilled. As a further result thereof, the cutting arrangement provides conditions for operating a lawnmower comprising the cutting arrangement in a more cost-efficient manner.

Accordingly, a cutting arrangement is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.

Optionally, the first radial distance is within the range of 150% - 1300% of the second radial distance or is within the range of 350% - 900% of the second radial distance. Thereby, it can be further ensured that at least a great proportion of the grass will have time to raise to an upright straight position by its own stiffness after having been bent by the front section of the cutting guard which improves the cutting result and provides conditions for an energy efficient cutting arrangement.

Optionally, a portion of the front section located radially outside of the circular path comprises a surface normal substantially parallel to a rotation plane of the cutting unit. Thereby, a safe and reliable cutting guard is provided. As an example, objects thrown from the cutting unit can bounce of the cutting guard in safe directions.

Optionally, the cutting guard comprises a side section enclosing a portion of the circular path, and wherein the first radial distance is greater than a third radial distance from the circular path to an inner surface of the side section of the cutting guard. Thereby, conditions are provided for forming a negative pressure inside the cutting guard using a low amount of energy while ensuring that at least a larger proportion of the grass can have time to raise to an upright straight position by its own stiffness after having been bent by the front section of the cutting guard during movement of the cutting guard in the forward direction. This is because of the relatively smaller distances between the circular path and the inner surface of the side section and the inner surface of the rear section as compared to the distance between the circular path and the inner surface of the front section. As a result thereof, conditions are provided for forming a negative pressure inside the cutting guard using a low amount of energy.

Optionally, the third radial distance is greater than the second radial distance. Thereby, conditions are provided for forming a negative pressure inside the cutting guard using a low amount of energy while ensuring that at least a larger proportion of the grass can have time to raise to an upright straight position by its own stiffness after having been bent by the front section of the cutting guard. This is because of the relatively smaller distance between the circular path and the inner surface of the rear section as compared to the distance between the circular path and the inner surface of the side section of the cutting guard which provides conditions for forming a negative pressure inside the cutting guard using a low amount of energy.

Optionally, the radial distance from the circular path to an inner surface of cutting guard increases continuously from the side section of the cutting guard towards the front section of the cutting guard. Thereby, conditions are provided for forming a negative pressure inside the cutting guard using a low amount of energy while ensuring that at least a larger proportion of the grass can have time to raise to an upright straight position by its own stiffness after having been bent by the front section of the cutting guard during movement of the cutting guard in the forward direction. Moreover, conditions are provided for obtaining advantageous aerodynamical properties inside the cutting guard which can reduce the rotational resistance of the cutting unit and hence the energy consumption of the cutting unit.

Optionally, the cutting unit comprises a number of sharp cutting edges, and wherein a length of the cutting edge/edges is/are within the range of 12% - 50% of the radius of the circular path. Thereby, conditions are provided for an energy efficient operation of the cutting arrangement while the cutting arrangement has conditions for obtaining an improved cutting result. 6 Optionally, a length of the cutting edge/edges is/are within the range of 17% - 33% of the radius of the circular path. Thereby, conditions are provided for a further reduced cutting resistance of the cutting unit and hence for a further reduced energy consumption of the cutting arrangement.

Optionally, the cutting unit comprises a number of sharp cutting edges, and wherein a length of the cutting edge/edges is/are within the range of 20 - 80 mm. Thereby, conditions are provided for an energy efficient operation of the cutting arrangement while the cutting arrangement has conditions for obtaining an improved cutting result.

Optionally, the length of the cutting edge/edges is/are within the range of 35 - 65 mm. Thereby, conditions are provided for a further reduced cutting resistance of the cutting unit and hence for a further reduced energy consumption of the cutting arrangement.

Optionally, the radius of the circular path is within the range of 50 - 400 mm. According to some embodiments, the radius of the circular path is within the range of 150 - 250 mm.

Optionally, the first radial distance is within the range of 15 - 80 mm or is within the range of 25 - 45 mm. Thereby, it can be ensured that a large proportion of the grass can have time to raise to an upright straight position by its own stiffness after having been bent by the front section of the cutting guard.

Optionally, the second radial distance is within the range of 2 - 14 mm or is within the range of 4 - 9 mm. Thereby, conditions are provided for forming a negative pressure inside the cutting guard using a low amount of energy while ensuring that at least a larger proportion of the grass can have time to raise to an upright straight position by its own stiffness after having been bent by the front section of the cutting guard during movement of the cutting guard in the forward direction.

Optionally, the cutting guard comprises a discharge opening arranged to eject clippings in a main discharge direction being transversal to the forward direction of the cutting arrangement. Thereby, a cutting arrangement is provided having conditions for distributing clippings in an efficient manner to avoid the formation of accumulated clipping in strings or clumps on a lawn being operated. ln addition, a cutting arrangement is provided having conditions for avoiding accumulation of clippings inside the cutting guard which can reduce the need for removal of such clippings. As a further result thereof, a more reliable cutting arrangement is provided.

Optionally, the angle between the main discharge direction and the fonNard direction is within the range of 30 - 170 degrees or is within the range of 70 - 150 degrees. Thereby, a cutting arrangement is provided having conditions for distributing clippings in a further efficient manner to avoid the formation of accumulated clipping in strings or clumps on a lawn being operated.

Optionally, the width of the discharge opening, measured in a rotation plane of the cutting unit, is within the range of 50% - 150% of the radius of the circular path, or is within the range of 108% - 138% of the radius of the circular path. Thereby, a cutting arrangement is provided having conditions for distributing clippings in a further efficient manner to avoid the formation of accumulated clipping in strings or clumps on a lawn being operated. Moreover, due to the relatively large width of the discharge opening, the clippings can be ejected in an efficient manner while using a low amount of energy to rotate the cutting unit.

Optionally, the cutting guard comprises a side section enclosing a portion of the circular path, and wherein the side section is arranged at a first side of the cutting guard and the discharge opening is arranged at a second side of the cutting guard, and wherein the second side is opposite to the first side. Thereby, conditions are provided for forming a negative pressure inside the cutting guard using a low amount of energy while ensuring that at least a larger proportion of the grass can have time to raise to an upright straight position by its own stiffness after having been bent by the front section of the cutting guard during movement of the cutting guard in the forward direction.

Optionally, the cutting unit comprises one or more surfaces being angled relative to a rotation plane of the cutting unit to generate an airflow in a direction transverse to the rotation plane during operation of the cutting unit. Thereby, it can be further ensured that grass is lifted towards the cutting unit during operation of the cutting arrangement to further improve the cutting result. ln addition, it can be ensured that grass already bent when the cutting arrangement is moved over a lawn is lifted towards the cutting unit. However, since the cutting arrangement can ensure that a larger proportion of the grass will have time to raise to an upright straight position by its own stiffness, the need for using large angles of the surfaces is reduced. ln this manner, an energy efficient cutting arrangement can be provided having conditions for an improved cutting result.

Optionally, the surfaces are angled relative to the rotation plane to generate an airflow in a direction towards a top surface of the cutting guard during operation of the cutting unit. 8 Thereby, an airflow is generated in a direction from the ground surface towards the top surface of the cutting guard during operation of the cutting arrangement to efficiently lift grass towards the cutting unit.

Optionally, the cutting unit comprises a number of sharp cutting edges, and wherein each surface of the one or more surfaces is/are separate from the number of sharp leading edges. Thereby, an effective airflow and an effective generation of negative pressure inside the cutting guard can be ensured, while ensuring a satisfactory cutting result.

Optionally, the one or more surfaces is/are angled relative to the rotation p|ane with an angle within the range of 12 - 38 degrees, or within the range of 17 - 23 degrees. Thereby, due to the relatively small angle between the one or more surfaces and the rotation p|ane, a low rotational resistance of the cutting unit and hence a low energy consumption of the cutting unit is provided. Moreover, due to the relatively small angle between the one or more surfaces and the rotation p|ane, air flow in unwanted directions is reduced which in turn reduces the rotational resistance of the cutting unit and hence the energy consumption of the cutting arrangement.

Accordingly, due to the relatively small angle between the one or more surfaces and the rotation p|ane, a negative pressure inside the cutting guard can be generated in an efficient manner. ln addition, as understood from the above described, since the cutting arrangement can ensure that grass can have time to raise to an upright straight position by its own stiffness, a satisfactory cutting result can be obtained despite a lower negative pressure inside the cutting guard caused by the relatively small angle between the one or more surfaces and the rotation p|ane of the cutting unit.

Optionally, the cutting unit comprises at least a first and a second surface each being angled relative to the rotation p|ane of the cutting unit to generate an airflow in a direction transverse to the rotation p|ane during operation of the cutting arrangement, wherein the second surface is arranged behind the first surface along a tangential direction of the cutting unit, and wherein the first surface is angled at a first angle relative to the rotation p|ane and the second surface is angled at a second angle relative to the rotation p|ane, and wherein the second angle is greater than the first angle. Thereby, efficient aerodynamic properties of the cutting unit can be provided to efficiently generate a negative pressure inside the cutting guard while avoiding a high rotational resistance of the cutting unit. Accordingly, due to these features, an even more energy efficient cutting arrangement can be provided. 9 Optionally, the second surface is arranged behind the first surface seen along a moving direction of the surfaces upon rotation of the cutting unit in an intended rotational direction. Thereby, efficient aerodynamic properties of the cutting unit can be provided to efficiently generate a negative pressure inside the cutting guard while avoiding a high rotational resistance of the cutting unit. Accordingly, due to these features, an even more efficient cutting arrangement can be provided.

Optionally, the cutting unit comprises a first section comprising the first surface, and wherein the first section comprises a sharp leading edge arranged adjacent to the first surface. Thereby, a cutting unit is provided capable of efficiently generating a negative pressure inside the cutting guard while providing conditions for obtaining a satisfactory cutting result.

Optionally, the first angle is within the range of 1 - 12 degrees or is within the range of 2 - 7 degrees, and wherein the second angle is within the range of 12 - 38 degrees, or within the range of 17 - 23 degrees. Thereby, efficient aerodynamic properties of the cutting unit can be ensured to efficiently generate a negative pressure inside the cutting guard while avoiding high rotational resistance of the cutting unit. Accordingly, due to these features, an even more efficient cutting arrangement can be provided.

Optionally, each of the first and second surfaces is substantially planar. Thereby, a cutting arrangement is provided capable of efficiently generating a negative pressure inside the cutting guard and capable of cutting vegetation in an efficient manner while having conditions and characteristics suitable for being manufactured in a cost-efficient manner.

Optionally, the cutting unit comprises a hub and a number of cutting members pivotally attached at a periphery of the hub. Thereby, a safer and more durable cutting arrangement is provided because a cutting member may pivot upon impact with an object, such as a stone, a stump, or a limb of a person or animal.

Optionally, the one or more surfaces is/are surfaces of the cutting members. Thereby, a safer and more durable cutting arrangement is provided having conditions for efficiently generating a negative pressure inside the cutting guard.

Optionally, the hub is disc-shaped. Thereby, an even safer and more operational reliable cutting arrangement is provided. This is because a disc-shaped hub is considerably less likely to become stuck upon impact with an object, such as a stone, a stump, or a limb of a person or animal, as compared to a hub having another type of shape.

Optionally, the cutting unit comprising at least two cutting members arranged at different distances from a rotation axis of the cutting unit. Thereby, a cutting arrangement is provided having conditions for cutting vegetation in a further efficient manner. This is because the at least two cutting members will cut vegetation at different radiuses from the rotation axis of the cutting unit. According to these embodiments, the radially outer portion/portions of the cutting unit which orbits in the circu|ar path inside the cutting guard is/are portion/portions of a cutting member arranged furthest from the rotation axis.

Optionally, each cutting member comprises a first and a second section comprising a first and a second surface respectively, wherein each of the first and a second surfaces is angled relative to the rotation plane of the cutting unit to generate an airflow in a direction transverse to the rotation plane during operation of the cutting arrangement, and wherein each cutting member further comprises an attachment section pivotally attached to a hub of the cutting unit, and a connecting section connecting the first section to the attachment section. Thereby, a cutting arrangement is provided capable efficiently generating a negative pressure inside the cutting guard and capable of cutting vegetation in an efficient manner while having conditions and characteristics suitable for being manufactured in a cost-efficient mannef.

Optionally, the attachment section is parallel to the rotation plane. Thereby, a cutting arrangement is provided capable of efficiently generating a negative pressure inside the cutting guard and capable of cutting vegetation in an efficient manner while having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient mannef.

Optionally, the connecting section is angled relative to the rotation plane and relative to a radial direction of the cutting unit. Thereby, a cutting arrangement is provided having conditions for cutting vegetation in a further efficient manner.

Optionally, the first section, the second section, the attachment section, and the connecting section are formed by bending of one piece of a sheet material. Thereby, a cutting arrangement is provided capable of efficiently generating a negative pressure inside the cutting guard and capable of cutting vegetation in an efficient manner while having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient mannef. 11 Optionally, each of the first section, the second section, the attachment section, and the connecting section is substantially planar. Thereby, a cutting arrangement is provided capable efficiently generating a negative pressure inside the cutting guard and capable of cutting vegetation in an efficient manner while having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient manner.

According to a second aspect of the invention, the object is achieved by a lawnmower comprising a cutting arrangement according to some embodiments of the present disclosure. Thereby, a lawnmower is provided having conditions for cutting grass in an energy efficient manner while having conditions for obtaining an improved cutting result. The cutting result can be improved because grass is allowed to raise to an upright straight position by its own stiffness after having been bent by the front section of the cutting guard during movement of the lawnmower in the forward direction over a lawn.

Moreover, the need for forming a large negative pressure inside the cutting guard is circumvented, or at least reduced, which provides conditions for operating the lawnmower in an energy efficient manner. ln addition, the greater distance from the front section of the cutting guard to the circular path can reduce the negative pressure inside the cutting guard which in turn can reduce the rotational resistance of the cutting unit and hence the energy consumption of the lawnmower.

Thus, due to the features of the cutting arrangement of the lawnmower, the energy consumption of the lawnmower can be lowered, and the cutting result can be improved. As a further result thereof, a lawnmower is provided having conditions for more available operational time before an energy storing unit of the lawnmower has to be charged or refilled. ln addition, a more cost-efficient lawnmower is provided.

Accordingly, a lawnmower is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.

Optionally, the lawnmower is a self-propelled robotic lawnmower configured to navigate and cut grass in an area in an autonomous manner. Thereby, a self-propelled robotic lawnmower is provided having conditions for cutting grass in an energy efficient manner while having conditions for obtaining an improved cutting result. The cutting result can be improved because grass is allowed to raise to an upright straight position by its own stiffness after 12 having been bent by the front section of the cutting guard during movement of the lawnmower in the fonNard direction over a lawn.

I\/|oreover, the need for forming a large negative pressure inside the cutting guard is circumvented, or at least reduced, which provides conditions for operating the self-propelled robotic lawnmower in an energy efficient manner. ln addition, the greater distance from the front section of the cutting guard to the circular path can reduce the negative pressure inside the cutting guard which in turn can reduce the rotational resistance of the cutting unit and hence the energy consumption of the self-propelled robotic lawnmower.

Thus, due to the features of the cutting arrangement of the self-propelled robotic lawnmower, the energy consumption of the self-propelled robotic lawnmower can be lowered, and the cutting result can be improved. As a further result thereof, a self-propelled robotic lawnmower is provided having conditions for more available operational time. ln addition, a more cost- efficient self-propelled robotic lawnmower is provided.

Optionally, the lawnmower comprises a motor configured to rotate the cutting unit during operation of the lawnmower at a rotational speed causing the one or more radially outer portions of the cutting unit to orbit at a velocity within the range of 60 - 80 metres per second, or within the range of 65 - 75 metres per second. Thereby, a low energy consumption of the cutting unit can be ensured while obtaining a satisfactory cutting result.

Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS Various aspects of the invention, including its particularfeatures and advantages, will be readily understood from the example embodiments discussed in the following detailed description and the accompanying drawings, in which: Fig. 1 illustrates a perspective view of a lawnmower according to some embodiments of the present disclosure, Fig. 2 illustrates a perspective view of an underside of the lawnmower illustrated in Fig. 1, Fig. 3 illustrates an enlarged view of a cutting arrangement of the lawnmower illustrated in Fig. 1 and Fig. 2, Fig. 4 illustrates a cross section of the cutting arrangement illustrated in Fig. 3, 13 Fig. 5 illustrates a perspective view of a cutting member of a cutting unit according to the embodiments illustrated in Fig. 1 - Fig. 4, Fig. 6 illustrates a side view of the cutting member illustrated in Fig. 5, Fig. 7 illustrates a perspective view of a cutting arrangement according to some further embodiments, Fig. 8 illustrates a cutting arrangement according to some further embodiments, and Fig. 9 illustrates a cross section of the cutting arrangement illustrated in Fig. 8.

DETAILED DESCRIPTION Aspects of the present invention will now be described more fully. Like numbers refer to like elements throughout. Well-known functions or constructions will not necessarily be described in detail for brevity and/or clarity.

Fig. 1 illustrates a perspective view of a lawnmower 1 according to some embodiments of the present disclosure. According to the illustrated embodiments, the lawnmower 1 is a self- propelled autonomous robotic lawnmower, i.e. a lawnmower 1 capable of navigating and operating an area in an autonomous manner in an area without the intervention or the direct control of a user. For reasons of brevity and clarity, the self-propelled autonomous robotic lawnmower 1 is in some places herein referred to as “the robotic lawnmower 1” or simply “the lawnmower 1”. According to further embodiments, the lawnmower 1 may be another type of lawnmower, such as a walk-behind mower or a push mower. According to the embodiments herein, the lawnmower 1 is a small or mid-sized lawnmower 1 configured to be used to cut grass in areas used for aesthetic and recreational purposes, such as gardens, parks, city parks, sports fields, lawns around houses, apartments, commercial buildings, offices, and the like.

The lawnmower 1 comprises a lawnmower body 30 and a number of lawnmower support members 41,41' each configured to abut against a ground surface 32 in a first plane P1 during operation of the lawnmower 1 to support the lawnmower body 30. The lawnmower body 30, as referred to herein, may also be referred to as a lawnmower chassis. Accordingly, the first plane P1 will extend along a ground surface 32 when the lawnmower 1 is positioned on a flat ground surface 32 in an intended use position thereon as is illustrated in Fig. 1.

According to the illustrated embodiments, the lawnmower support members 41, 41' is wheels 41, 41' of the lawnmower 1. According to the illustrated embodiments, the lawnmower1 comprises four wheels 41, 41', namely two drive wheels 41 and two support wheels 41”. The 14 drive wheels 41 of the lawnmower 1 may each be powered by an electrical motor of the lawnmower 1 to provide motive power and/or steering of the lawnmower 1. ln Fig. 1, a longitudinal direction Id of the lawnmower1 is indicated. The longitudinal direction Id of the lawnmower 1 extends in a longitudinal p|ane of the lawnmower 1. The longitudinal p|ane is parallel to the first p|ane P1. The longitudinal direction Id of the lawnmower1 is thus parallel to the first p|ane P1 and thus also to a ground surface 32 when the lawnmower1 is positioned onto a flat ground surface 32 in an intended use position as is illustrated in Fig. 1. Moreover, the longitudinal direction Id of the lawnmower 1 is parallel to a forward direction fd' of the lawnmower 1 as well as a reverse direction of the lawnmower 1. The reverse direction is opposite to the forward direction fd'. The forward direction fd' of the lawnmower 1 may also be referred to as a forward moving direction fd' of the lawnmower 1. Likewise, the reverse direction of the lawnmower 1 may also be referred to as a reverse moving direction of the lawnmower 1 According to the illustrated embodiments, the drive wheels 41 of the lawnmower 1 are non- steered wheels having a fix rolling direction in relation to the lawnmower body 30. The respective rolling direction of the drive wheels 41 of the lawnmower 1 is substantially parallel to the longitudinal direction Id of the lawnmower 1. According to the illustrated embodiments, the support wheels 41' are non-driven wheels. Moreover, according to the illustrated embodiments, the support wheels 41' can pivot around a respective pivot axis such that the rolling direction of the respective support wheel 41' can follow a travel direction of the lawnmower 1.

As understood from the above, when the drive wheels 41, 41' of the lawnmower 1 are rotated at the same rotational velocity in a forward rotational direction, and no wheel slip is occurring, the lawnmower1 will move in the fonNard direction fd' indicated in Fig. 1. Likewise, when the drive wheels 41, 41' of the lawnmower 1 are rotated at the same rotational velocity in a reverse rotational direction, and no wheel slip is occurring, the lawnmower 1 will move in the reverse direction.

According to the illustrated embodiments, the lawnmower 1 may be referred to as a four- wheeled rear wheel driven lawnmower 1. According to further embodiments, the lawnmower 1 may be provided with another number of wheels 41, 41 ', such as three wheels. Moreover, according to further embodiments, the lawnmower 1 may be provided with another configuration of driven and non-driven wheels, such as a front wheel drive or an all-wheel drive.

According to the illustrated embodiments, the lawnmower 1 comprises a control arrangement 28. The control arrangement 28 may be configured to control propulsion of the lawnmower 1, and steer the lawnmower 1, by controlling electrical motors of the lawnmower 1 arranged to drive the drive wheels 41 of the lawnmower 1. According to further embodiments, the control arrangement 28 may be configured to steer the lawnmower 1 by controlling the angle of steered wheels of the lawnmower 1. According to still further embodiments, the robotic lawnmower may be an articulated robotic lawnmower, wherein the control arrangement 28 may be configured to steer the robotic lawnmower by controlling the angle betvveen frame portions of the articulated robotic lawnmower.

The control arrangement 28 may be configured to control propulsion of the lawnmower 1 and may be configured to steer the lawnmower 1 so as to navigate the lawnmower 1 in an area to be operated. The lawnmower 1 may further comprise one or more sensors arranged to sense a magnetic field of a wire, and/or one or more positioning units, and/or one or more sensors arranged to detect an impending or ongoing collision event with an object. ln addition, the lawnmower 1 may comprise a communication unit connected to the control arrangement 28. The communication unit may be configured to communicate with a remote communication unit to receive instructions therefrom and/or to send information thereto. The communication may be performed wirelessly over a wireless connection such as the internet, or a wireless local area network (WLAN), or a cellular network, or a wireless connection for exchanging data over short distances using short-wavelength, i.e. ultra-high frequency (UHF) radio waves in the industrial, scientific, and medical (ISM) band from 2.4 to 2.486 GHz.

The control arrangement 28 may be configured to control propulsion of the lawnmower 1, and steer the lawnmower 1, so as to navigate the lawnmower 1 in a systematic and/or random pattern to ensure that an area is completely covered, using input from one or more of the above described sensors and/or units. Furthermore, the lawnmower 1 may comprise one or more batteries arranged to supply electricity to components of the lawnmower 1. As an example, the one or more batteries may be arranged to supply electricity to electrical motors of the lawnmower 1, such as one or more electric propulsion motors, by an amount controlled by the control arrangement 28. The lawnmower 1 comprises a cutting arrangement 2. The cutting arrangement 2 is configured to cut vegetation, such as leaves, as is further explained herein.

Fig. 2 illustrates a perspective view of an underside of the lawnmower 1 illustrated in Fig. 1.

As indicated in Fig. 2, the cutting arrangement 2 comprises a cutting guard 3 and a cutting 16 unit 4. The cutting arrangement 2 is configured to be attached to a lawnmower 1 to cut vegetation, such as grass. The cutting arrangement 2 is configured to be attached to the lawnmower 1 such that a forward direction fd of the cutting arrangement 2 coincides with the forward direction fd' of the lawnmower 1. Accordingly, the cutting guard 3 is configured to be attached to the lawnmower body 30 in a predetermined orientation relative to the lawnmower body 30. The cutting arrangement 2 may be attached to the lawnmower 1 using one or more fastening elements, one or more snap-fit arrangements, or the like. The cutting unit 4 may be attached to a drive shaft of the lawnmower 1, which drive shaft is configured to rotate the cutting unit 4 when the lawnmower 1 is used for cutting grass. The cutting unit 4 may be attached to the drive shaft via a splined connection, or the like.

According to the embodiments i||ustrated in Fig. 2, the cutting unit 4 comprises a hub 16 and a number of cutting members 19 pivotally attached at a periphery of the hub 16. Moreover, according to these embodiments, the hub 16 is disc-shaped. According to further embodiments, the cutting unit 4 may be differently arranged and may have a different layout, as is further explained herein.

Fig. 3 illustrates an enlarged view of the cutting arrangement 2 of the lawnmower 1 i||ustrated in Fig. 1 and Fig. 2. The cutting unit 4 is configured to be rotated in an intended rotational direction Dr around a rotation axis AX of the cutting unit 4. ln Fig. 3, a rotation plane pr of the cutting unit 4 is indicated. The rotation plane pr of the cutting unit 4 is perpendicular to the rotation axis Ax and may also be referred to as a cutting plane of the cutting unit 4. ln Fig. 3, the cutting arrangement 2 is i||ustrated in a viewing direction perpendicular the rotation plane pr of the cutting unit 4. Below, simultaneous reference is made to Fig. 1 - Fig. 3, if not indicated othenNise.

The cutting arrangement 2 is configured such that the rotation plane pr of the cutting unit 4 is substantially parallel to a ground surface 32, and thus also to the first plane P1 referred to above, when a lawnmower 1 comprising the cutting arrangement 2 is positioned in an intended upright use position on a flat ground surface 32. The feature that the rotation plane pr of the cutting unit 4 is substantially parallel to a ground surface 32, and thus also to the first plane P1, may encompass that the angle between the rotation plane pr and the ground surface 32 is less than 15 degrees, or less than 10 degrees when a lawnmower 1 comprising the cutting arrangement 2 is positioned in an intended upright use position on a flat ground surface 32. Likewise, the feature that the rotation plane pr of the cutting unit 4 is substantially parallel to the first plane P1, may encompass that the angle between the rotation plane pr and the first plane P1 is less than 15 degrees, or less than 10 degrees. 17 Thus, as understood from the above, according to the illustrated embodiments, the rotation axis Ax is substantially perpendicular to the first plane P1 and thus also substantially perpendicular to a ground surface 32 when the lawnmower 1 is positioned onto a flat ground surface 32 in the intended use position. According to some embodiments, the angle bet\Neen the rotation axis AX and the first plane P1 may be within the range of 82 degrees - 98 degrees or may be within the range of 85 degrees - 95 degrees.

The cutting unit 4 of the cutting arrangement 2 is configured to rotate such that one or more radially outer portions 4' of the cutting unit 4 orbits in a circu|ar path C inside the cutting guard 3. As understood from the above described, the circu|ar path C extends in the rotation plane pr of the cutting unit 4. The circu|ar path C, as referred to herein, is a geometric shape which can be obtained by tracing the circu|ar movement of one or more radially outer portions 4' of the cutting unit 4 upon rotation of the cutting unit 4 inside the cutting guard 3.

As indicated in Fig. 3, the cutting guard 3 comprises a front section 5 and a rear section 6, seen relative to the forward direction fd of the cutting arrangement 2. The front section 5 and the rear section 6 together enc|oses a portion of the cutting unit 4 and also a portion of the circu|ar path C. The front section 5 may be the foremost part of the cutting guard 3 and the rear section 6 may be the rearmost part of the cutting guard 3, seen relative to the fon/vard direction fd of the cutting arrangement 2. During movement of a lawnmower 1 comprising the cutting arrangement 2 in the forward direction fd', grass or other type of vegetation will first reach the front section 5 of the cutting guard 3. The front section 5 of the cutting guard 3 may also be referred to as a leading section of the cutting guard 3 seen relative to the fonNard direction fd of the cutting arrangement 2 and the rear section 6 of the cutting guard 3 may also be referred to as a trailing section of the cutting guard 3 seen relative to the fon/vard direction fd of the cutting arrangement 2.

As can be clearly seen in Fig. 3, the cutting arrangement 2 is arranged such that a first radial distance r1 from the circu|ar path C to an inner surface 5' of the front section 5 of the cutting guard 3 is greater than a second radial distance r2 from the circu|ar path C to an inner surface 6' of the rear section 6 of the cutting guard 3. The first radial distance r1 as referred to herein may be defined as the distance from the circu|ar path C to an inner surface 5' of the front section 5 of the cutting guard 3 measured in a radial direction rd of the circu|ar path C. Likewise, the second radial distance r2 as referred to herein may be defined as the distance from the circu|ar path C to a radially inner delimiting surfaces 6' of the rear section 6 of the cutting guard 3 measured in a radial direction rd of the circu|ar path C. As understood from 18 the herein described, the radial direction rd of the circular path C is perpendicular to the rotation aXis AX of the cutting unit 4 and eXtends in the rotation plane pr of the cutting unit 4. Moreover, the radial direction rd of the circular path C coincides with a radial direction rd of the cutting unit 4. Furthermore, according to the illustrated embodiments, the radial direction rd of the cutting unit 4 coincides with a radial direction rd of the cutting guard 3. ln addition, as understood from the above described, the first radial distance r1 can be obtained by subtracting the radius r of the circular path C from the distance between the rotation aXis AX of the cutting unit 4 and the inner surface 5' of the front section 5 of the cutting guard 3. Likewise, the second radial distance r2 can be obtained by subtracting the radius r of the circular path C from the distance between the rotation aXis AX of the cutting unit 4 and the inner surface 6' of the rear section 6 of the cutting guard 3. The radius r of the circular path C can also be referred to the radius r of the cutting unit 4 measured from the rotation aXis AX of the cutting unit 4 to a radially outer portion 4' of the cutting unit 4.

Fig. 4 illustrates a cross section of the cutting arrangement 2 illustrated in Fig. 3. ln Fig. 4, the cross section is made in a plane comprising the rotation aXis AX of the cutting unit 4. ln other words, in Fig. 4, the cross section is made in a plane perpendicular to the rotation plane pr of the cutting unit 4. ln Fig. 4, the first and second radial distances r1, r2 are indicated. According to the embodiments illustrated in Fig. 3 and Fig. 4, the first radial distance r1 is approXimate|y five times larger than the second radial distance r2. ln other words, according to the embodiments illustrated in Fig. 3 and Fig. 4, the first radial distance r1 is approXimate|y 500% of the second radial distance r2. According to further embodiments, the first radial distance r1 may be within the range of 150% - 1300% of the second radial distance r2 or may be within the range of 350% - 900% of the second radial distance r2.

Since the first radial distance r1 is greater than the second radial distance r2, a cutting arrangement 2 is provided having conditions for cutting grass in an energy efficient manner while having conditions for obtaining an improved cutting result. The cutting result can be improved because grass is allowed to raise to an upright straight position by its own stiffness after having been bent by the front section 5 of the cutting guard 3 during movement of the cutting guard 3 in the forward direction fd over a lawn. That is, when the cutting arrangement 2 is moved in the forward direction fd indicated in Fig. 4 over a lawn, i.e. to the right in Fig. 4, the front section 5 of the cutting guard 3 will bend grass. Studies have shown that the bending of the grass caused by a front section of a cutting guard impairs the cutting result because a large proportion of the grass do not have time to raise to an upright straight 19 position by its own stiffness to reach the cutting unit during cutting. However, due to the relatively large distance r1 from the inner surface 5' of the front section 5 and radially outer portions 4' of the cutting arrangement 2, grass is allowed to raise to an upright straight position by its own stiffness after having been bent by the front section 5 to reach the cutting unit 4. ln this manner, the cutting result can be improved.

Moreover, the need for forming a large negative pressure inside the cutting guard 3 is circumvented, or at least reduced, which provides conditions for operating the cutting arrangement 2 in an energy efficient manner. ln addition, the greater distance from the front section 5 of the cutting guard 3 to the circular path C can reduce the negative pressure inside the cutting guard 3 which in turn can reduce the rotational resistance of the cutting unit 4 and hence the energy consumption of the cutting arrangement 2.

Thus, due to the features of the cutting arrangement 2, the energy consumption of a lawnmower 1 comprising the cutting arrangement 2 can be lowered and the cutting result can be improved. ln addition, the cutting arrangement 2 provides conditions for increasing available operational time of a lawnmower comprising the cutting arrangement 2 before an energy storing unit of the lawnmower has to be charged or refilled. As a further result thereof, the cutting arrangement 2 provides conditions for operating the lawnmower 1 comprising the cutting arrangement 2 in a more cost-efficient manner.

As indicated in Fig. 4, according to the illustrated embodiments, the cutting unit 4 comprises a number of surfaces 22' being angled relative to a rotation plane Pr of the cutting unit 4 to generate an airflow in a direction d1 transverse to the rotation plane Pr during operation of the cutting unit 4. According to the illustrated embodiments, the surfaces 22' are angled relative to the rotation plane Pr to generate an airflow in a direction d1 towards a top surface 13 of the cutting guard 3 during operation of the cutting unit 4. ln this manner, a negative pressure can be generated inside the cutting guard 3 in an efficient manner to further ensure that grass is lifted towards the cutting unit 4 during operation of the cutting arrangement 2. However, due to the relatively large distance r1 from the inner surface 5' of the front section 5 and radially outer portions 4' of the cutting arrangement 2, the surfaces 22' can be provided with relatively small angles relative to the rotation plane Pr of the cutting unit 4 while ensuring a satisfactory cutting result.

By using relatively small angles between the one or more surfaces 22' and the rotation plane pr, a low rotational resistance of the cutting unit 4 and hence a low energy consumption of the cutting unit 4 is provided. Moreover, small angles between the one or more surfaces 22' and the rotation plane pr lower air flow in unwanted directions which in turn reduces the rotational resistance of the cutting unit 4 and hence the energy consumption of the cutting arrangement 2. ln addition, as understood from the above described, since the cutting arrangement 2 can ensure that grass can have time to raise to an upright straight position by its own stiffness, a satisfactory cutting result can be obtained despite a lower negative pressure inside the cutting guard 3 caused by the relatively small angle betvveen the one or more surfaces 22' and the rotation plane pr of the cutting unit 4. The features, functions, and advantages of the one or more surfaces 21 'of the cutting arrangement 2 are further explained below. ln Fig. 4, a centre aXis Ca of the cutting guard 3 is indicated. The centre aXis Ca of the cutting guard 3 extends through a centre of the cutting guard 3 in a direction parallel to the rotation aXis AX of the cutting unit 4. The distance between the centre aXis Ca and the inner surface 5' of the front section 5 is thus the same as the distance between the centre aXis Ca and the inner surface 6' of the rear section 6 of the cutting guard 3. As clearly seen in Fig. 4, the rotation aXis AX of the cutting unit 4 is displaced relative the centre aXis Ca in a direction towards the rear section 6 of the cutting guard 3. ln other words, the rotation aXis AX of the cutting unit 4 is closer to the rear section 6 of the cutting guard 3 than the centre aXis Ca of the cutting guard 3.

As indicated in Fig. 4, according to the illustrated embodiments, the portion 5” of the front section 5 located radially outside of the circular path C comprises a surface normal N substantially parallel to a rotation plane Pr of the cutting unit 4. Thereby, a safe and reliable cutting guard 3 is provided. As an example, objects thrown from the cutting unit 4 towards the cutting guard 3 can bounce of the cutting guard 3 in safe directions.

As mentioned above, according to the embodiments illustrated in Fig. 1 - Fig. 4, the cutting unit 4 comprises a hub 16 and a number of cutting members 19 pivotally attached at a periphery of the hub 16. ln Fig. 4, a pivot aXis pA of one cutting member 19 is indicated. According to the illustrated embodiments, the pivot aXis pA is substantially parallel to the rotation aXis AX of the cutting unit 4. According to the embodiments illustrated in Fig. 1 - Fig. 4, the cutting unit 4 comprises two cutting members 19 pivotally attached at a periphery of the hub 16. According to further embodiments, the cutting unit 4 may comprise another number of cutting members 19, such as one, three, four, five, or the like.

According to some embodiments, the cutting unit 4 may comprise at least two cutting members 19 arranged at different distances from a rotation aXis AX of the cutting unit 4. 21 Thereby, a cutting arrangement 2 is provided having conditions for cutting vegetation in a further efficient manner. This is because the at least two cutting members 19 will cut vegetation at different radiuses from the rotation axis AX of the cutting unit 4. According to the illustrated embodiments, the one or more surfaces 22' referred to above is/are surfaces 22' of the cutting members 19.

Fig. 5 illustrates a perspective view of a cutting member 19 of the cutting unit 4 according to the embodiments illustrated in Fig. 1 - Fig. 4. Below, simultaneous reference is made to Fig. 1 - Fig. 5, if not indicated otherwise. The cutting member 19 comprises an attachment section 24. The cutting member 19 is configured to be pivotally attached to a hub 16 of the cutting unit 4 around the pivot axis pA. According to the illustrated embodiments, the attachment section 24 comprises a through hole 55. According to the illustrated embodiments, the cutting member 19 is configured to be pivotally attached to the hub 16 by a fastening element extending through the through hole 55.

The cutting member 19 further comprises a first and a second section 21, 22 comprising a first and a second surface 21 ', 22' respectively. That is, the first section 21 of the cutting member 19 comprises the first surface 21' and the second section 22 of the cutting member 19 comprises the second surface 22'. Each of the first and a second surfaces 21', 22' is angled relative to the rotation plane Pr of the cutting unit 4 to generate an airflow in a direction d1 transverse to the rotation plane Pr during rotation of the cutting arrangement 2.

Fig. 6 illustrates a side view of the cutting member 19 illustrated in Fig. 5. Below, simultaneous reference is made to Fig. 1 - Fig. 6, if not indicated othenNise. ln Fig. 5 and Fig. 6, a moving direction md of the cutting member 19 is indicated. The cutting member 19 moves in the moving direction md upon rotation of the cutting unit 4 in the intended rotational direction Dr indicated in Fig. 3. Obviously, the moving direction md is parallel to the rotation plane Pr of the cutting unit 4 and is perpendicular to a radial direction rd of the cutting unit 4. Moreover, the moving direction md of the cutting unit 4 is parallel to a tangential direction Td of the cutting unit 4.

As best seen in Fig. 5 and Fig. 6, according to the illustrated embodiments, the second surface 22' is arranged behind the first surface 21' seen along the moving direction md of the surfaces 21', 22' upon rotation of the cutting unit 4 in an intended rotational direction Dr. ln other words, the second surface 22' is arranged at a trailing edge of the first surface 21' seen along the moving direction md of the surfaces 21', 22' upon rotation of the cutting unit 4 in an intended rotational direction Dr. Moreover, as indicated in Fig. 6, the first surface 21' is 22 angled at a first angle a1 relative to the rotation plane Pr and the second surface 22' is angled at a second angle a2 relative to the rotation plane Pr, and wherein the second angle a2 is greater than the first angle a1. Thereby, efficient aerodynamic properties of the cutting member 19 is provided to efficiently generate a negative pressure inside the cutting guard 3 while avoiding a high rotational resistance of the cutting unit 4. Accordingly, due to these features, an even more efficient cutting arrangement 2 is provided.

According to the illustrated embodiments, the first angle a1 is approximately 5 degrees and the second angle a2 is approximately 20 degrees. Thus, according to the illustrated embodiments, the angle between the first and second surfaces 21 ', 22' is approximately 15 degrees. According to further embodiments, the first angle a1 may be within the range of 0 - 12 degrees, or may be within the range of 2 - 7 degrees, and the second angle a2 may be within the range of 12 - 38 degrees or may be within the range of 17 - 23 degrees. ln this manner, a negative pressure inside the cutting guard 3 can be generated in an efficient manner while avoiding a high rotational resistance of the cutting unit 4.

The cutting member 19 comprises a sharp leading edge 17, i.e. a sharp edge at a front section of the cutting member 19 seen in the moving direction md of the cutting member 19. As seen in Fig. 5 and Fig. 6, the first and second surfaces 21', 22' are each separate from each of the number of sharp leading edges 17. Moreover, according to the illustrated embodiments, the first section 21 of the cutting member 19 comprises the sharp leading edge 17, wherein the sharp leading edge 17 is arranged adjacent to the first surface 21'. The sharp leading edge 17 is configured to cut vegetation upon rotation of the cutting unit 4.

As best seen in Fig. 6, according to the illustrated embodiments, the attachment section 24 of the cutting member 19 is parallel to the rotation plane Pr. Moreover, the cutting member 19 comprises a connecting section 25 connecting the first section 21 to the attachment section 24. The second section 22 is attached to the attachment section 24 via the first section 21. As can be seen in Fig. 5 and Fig. 6, according to the illustrated embodiments, the connecting section 25 is angled relative to the rotation plane Pr and relative to a radial direction rd of the cutting unit 4. Moreover, according to the illustrated embodiments, the first section 21, the second section 22, the attachment section 24, and the connecting section 25 are formed by bending of one piece of a sheet metal material. Moreover, each of the first section 21, the second section 22, the attachment section 24, and the connecting section 25 is substantially planar. Thus, according to the illustrated embodiments, each of the first and second surfaces 21 ', 22' is substantially planar. Due to these features, a cutting member 19 is provided having conditions for cutting vegetation in an efficient manner while having 23 conditions and Characteristics suitable for being manufactured and assembled in a cost- efficient manner.

Even though the cutting member 19 according to the illustrated embodiments comprises t\No surfaces 21', 22' having different angles relative to the rotation plane Pr of the cutting unit 4, the cutting members 19 of the cutting unit 4 may comprise only one surface angled relative to the rotation plane Pr of the cutting unit. According to such embodiments, the angle bet\Neen such a surface and the rotation plane pr of the cutting unit 4 may be within one of the herein given ranges for the first and second angles a1, a2.

As indicated in Fig. 3, the cutting guard 3 comprises a side section 7 and a discharge opening 23. The side section 7 encloses a portion of the circular path C. ln more detail, according to the illustrated embodiments, the front section 5, the side section 7, and the rear section 6 together encloses approximately 75% of the circumference of the circular path C. The side section 7 is arranged at a first side S1 of the cutting guard 3 and the discharge opening 23 is arranged at a second side S2 of the cutting guard 3. The second side S2 of the cutting guard 3 is opposite to the first side S1 of the cutting guard 3.

As indicated in Fig. 3, the discharge opening 23 of the cutting guard 3 is arranged to eject clippings in a main discharge direction dm being transversal to the forward direction fd of the cutting arrangement 2. The main discharge direction dm is the main direction in which the discharge opening 23 discharges clippings from the cutting guard 3. According to the illustrated embodiments, the angle ad between the main discharge direction dm and the forward direction fd is approximately 90 degrees. According to further embodiments, the angle ad betvveen the main discharge direction dm and the fon/vard direction fd may be within the range of 30 - 170 degrees or may be within the range of 70 - 150 degrees.

As seen in Fig. 3, the discharge opening 23 is provided with a relatively large width w measured in the rotation plane Pr of the cutting unit 4. According to the illustrated embodiments, the width w of the discharge opening 23, measured in the rotation plane Pr of the cutting unit 4, is approximately 123% of the radius r of the circular path C. According to further embodiments, the width w of the discharge opening 23, measured in a rotation plane Pr of the cutting unit 4, may be within the range of 50% - 150% of the radius r of the circular path C, or may be within the range of 108% - 138% of the radius r of the circular path C.

Due to the features of the discharge opening 23, a cutting arrangement 2 is provided having conditions for distributing clippings in an efficient manner to avoid the formation of 24 accumulated clipping in strings or clumps on a lawn being operated. Moreover, due to the relatively large width w of the discharge opening 23, the clippings can be ejected in an efficient manner while using a low amount of energy for rotating the cutting unit 4.

The discharge opening 23 can also be seen in Fig. 1 and Fig. 2. According to the embodiments illustrated in Fig. 1 - Fig. 3, the discharge opening 23 is open to the surroundings. However, according to further embodiments, the discharge opening 23 may be provided with a deflecting section downstream of the discharge opening 23 illustrated in Fig. 1 - Fig. 3. Such a deflecting section may have a wall angled relative to the main discharge direction dm indicated in Fig. 3 to deflect matter flowing through the discharge opening 23. Such a wall may be configured to deflect matter in a direction opposite to the forward direction fd of the cutting guard 3. ln Fig. 3, a third radial distance r3 from the circular path C to an inner surface 7' of the side section 7 is indicated. The third radial distance r3 as referred to herein may be defined as the distance from the circular path C to the inner surface 7' of the side section 7 of the cutting guard 3 measured in a radial direction rd of the circular path C. ln addition, as understood from the above described, the third radial distance r3 can be obtained by subtracting the radius r of the circular path C from the distance between the rotation axis AX of the cutting unit 4 and inner surface 7' of the side section 7 of the cutting guard 3.

As can be seen in Fig. 3, the first radial distance r1 is greater than the third radial distance r3. Moreover, the third radial distance r3 is greater than the second radial distance r2. Thereby, conditions are provided for forming a negative pressure inside the cutting guard 3 using a low amount of energy while ensuring that at least a larger proportion of the grass can have time to raise to an upright straight position by its own stiffness after having been bent by the front section 5 of the cutting guard 3. A negative pressure inside the cutting guard 3 can be formed using a low amount of energy because of the relatively smaller distance r2 between the circular path C and the inner surface 6' of the rear section 6 as compared to the distance between the circular path C and the inner surface 7' of the side section 7 of the cutting guard 3.

Moreover, as can be seen in Fig. 3, the radial distance r3, r3', r1 from the circular path C to an inner surface 7', 3', 5' of cutting guard 3 increases continuously from the side section 7 of the cutting guard 3 towards the front section 5 of the cutting guard 3. ln addition, according to the illustrated embodiments, the radial distance r2, r3, from the circular path C to an inner surface 6', 7' of cutting guard 3 increases continuously from the rear section 6 of the cutting guard 3 towards the side section 7 of the cutting guard 3. Due to these features, conditions are provided for forming a negative pressure inside the cutting guard 3 using a low amount of energy while ensuring that at least a larger proportion of the grass can have time to raise to an upright straight position by its own stiffness after having been bent by the front section 5 of the cutting guard 3 during movement of the cutting guard 3 in the forward direction fd. Moreover, conditions are provided for obtaining advantageous aerodynamical properties inside the cutting guard 3 which can reduce the rotationa| resistance of the cutting unit 4 and hence the energy consumption of the cutting unit 4.

According to the i||ustrated embodiments, the radius r of the circu|ar path C is 200 mm. According to further embodiments, the radius r of the circu|ar path C may be within the range of 50 - 400 mm or within the range of 150 - 250 mm. Moreover, according to the i||ustrated embodiments, the length L of the cutting edges 17 of the cutting unit 4 is approximately 58 mm. According to further embodiments, the length L of the cutting edges 17 may be within the range of 20 - 80 mm, or within the range of 35 - 65 mm. Moreover, the length L of the cutting edges 17 may be within the range of 12% - 50% of the radius r of the circu|ar path C or may be within the range of 17% - 33% of the radius r of the circu|ar path C.

Moreover, according to the i||ustrated embodiments, the first radial distance r1 is approximately 35 mm. According to further embodiments, the first radial distance r1 may be within the range of 15 - 80 mm, or may be within the range of 25 - 45 mm. Furthermore, according to the i||ustrated embodiments, the second radial distance r2 is approximately 7 mm. According to further embodiments, the second radial distance r2 may be within the range of 2 - 14 mm, or may be within the range of 4 - 9 mm. Moreover, according to the i||ustrated embodiments, the third radial distance r3 is approximately 10 mm. According to further embodiments, the second radial distance r2 may be within the range of 5 - 20 mm, or may be within the range of 7 - 13 mm. ln Fig. 4, a motor 31 of the cutting arrangement 2 is indicated. The motor 31 is configured to rotate the cutting unit 4 during operation of the lawnmower 1. The motor 31 may be comprised in a lawnmower 1 comprising the cutting arrangement 2. According to the i||ustrated embodiments, the motor 31 is an electric motor. According to further embodiments, the motor 31 may be another type of motor for rotating the cutting unit 4, such as an internal combustion engine.

According to the i||ustrated embodiments, the motor 31 is configured to rotate the cutting unit 4 during operation of the lawnmower 1 at a rotationa| speed causing the one or more radially 26 outer portions 4' of the cutting unit 4 to orbit at a ve|ocity of approximately 70 metres per second. According to further embodiments, the motor 31 may be configured to rotate the cutting unit 4 during operation of the lawnmower 1 at a rotational speed causing the one or more radially outer portions 4' of the cutting unit 4 to orbit at a ve|ocity within the range of 60 - 80 metres per second, or within the range of 65 - 75 metres per second.

Tests have shown that the cutting arrangement 2 according to the illustrated embodiments is able to reduce the energy needed for cutting with approximately 50% while ensuring a satisfactory cutting result. As explained herein, this is at least partly obtained by the combination of the relatively large distance r1 from the inner surface 5' of the front section 5 and radially outer portions 4' of the cutting arrangement 2 and the fact that the surfaces 21 ', 22' for generating airflow can be provided with relatively small angles relative to the rotation plane Pr of the cutting unit 4.

As understood from the above described, according to the embodiments illustrated in Fig. 2 - Fig. 6, the number of surfaces 21 ', 22' being angled relative to a rotation plane Pr of the cutting unit 4 to generate an airflow in a direction d1 transverse to the rotation plane Pr during operation of the cutting arrangement 2 are surfaces 21 ', 22' of the cutting members 19 of the cutting unit 4.

Fig. 7 illustrates a perspective view of a cutting arrangement 2 according to some further embodiments. The cutting arrangement 2 illustrated in Fig. 7 comprises the same features, functions, and advantages as the cutting arrangement 2 explained with reference to Fig. 1 - Fig. 6, with some differences explained below.

According to the embodiments illustrated in Fig. 7, the cutting arrangement 2 comprises a cutting unit 4 comprising a fix arm arrangement 57 instead of a hub and a number of cutting members pivotally attached to the hub. lnstead, the cutting arrangement 2 comprises a number of cutting sections 19' rigidly attached to a respective arm of the fix arm arrangement 57. According to the embodiments illustrated in Fig. 7, the cutting unit 4 comprises two cutting sections 19' rigidly attached to a respective arm of the fix arm arrangement 57. Each cutting section 19' may have identical form, features, functions and advantages as the form, features, functions and advantages of the cutting members 19 of the cutting arrangement 2 explained with reference to Fig. 1 - Fig. 6, except the pivoting feature of the cutting members 19 explained with reference to Fig. 2 - Fig. 6. 27 Moreover, the cutting arrangement 2 illustrated in Fig. 7 comprises a cutting guard 3 according to the embodiments explained with reference to Fig. 2 - Fig. 4. Therefore, the features, functions, and advantages of the cutting arrangement 2 illustrated in Fig. 7 are not further explained herein.

Fig. 8 illustrates a cutting arrangement 2 according to some further embodiments. The cutting arrangement 2 comprises a cutting guard 3 and a cutting unit 4 configured to rotate inside the cutting guard 3. The cutting unit 4 is configured to rotate in a rotation plane pr. The rotation plane pr of the cutting unit 4 is perpendicular to a rotation axis Ax of the cutting unit 4 and may also be referred to as a cutting plane of the cutting unit 4. ln Fig. 3, the cutting arrangement 2 is illustrated in a viewing direction perpendicular the rotation plane pr of the cutting unit 4.

The cutting arrangement 2 according to the embodiments illustrated in Fig. 8 may comprise the same features, functions, and advantages as the cutting arrangement 2 explained with reference to Fig. 1 - Fig. 6, with some differences explained below. According to the embodiments illustrated in Fig. 8, the cutting arrangement 2 is configured to mulch vegetation. Mulching is a process in which vegetation, such as grass clippings, leaves, and the like are separated into small pieces by cutting. The vegetation then falls down to the ground. Mulching is an environmental way to get rid of vegetation. The micro life in the soil, worms and other animals can pull down the small pieces of the vegetation in the lawn. The breakdown become new soil and it improves and fertilizes the soil at the same time.

Since the cutting arrangement 2 according to the embodiments illustrated in Fig. 8 is configured to mulch vegetation, the cutting arrangement 2 may also be referred to as a mulching arrangement. Likewise, the cutting unit 4 of the cutting arrangement 2 may also be referred to as a mulching unit and the cutting guard 3 of the cutting arrangement 2 may also be referred to as a mulching guard. However, since mulching is a process involving cutting, these components/arrangements are herein referred to as the cutting arrangement 2, the cutting unit 4, and the cutting guard 3.

Below, simultaneous reference is made to Fig. 1 and Fig. 8 if not indicated otherwise. ln Fig. 8, a fonNard direction fd of the cutting arrangement 2 is indicated. The cutting arrangement 2 is configured to be attached to a lawnmower 1 such that the fon/vard direction fd of the cutting arrangement 2 coincides with the fonNard direction fd' of the lawnmower 1. Accordingly, the cutting guard 3 is configured to be attached to the lawnmower body 30 in a predetermined orientation relative to the lawnmower body 30. The cutting arrangement 2 illustrated in Fig. 8 28 may be sold as a mulching kit comprising at least the cutting guard 3 and the cutting unit 5 which allows a user to convert a lawnmower1 into a mulching machine capable of mulching vegetation, such as leaves, grass clippings, or the like. The cutting arrangement 2 may be attached to the lawnmower 1 using one or more fastening elements, one or more snap-fit arrangements, or the like. The cutting unit 4 may be attached to a drive shaft of the lawnmower 1, which drive shaft is configured to rotate the cutting unit 4. The cutting unit 4 may be attached to the drive shaft via a splined connection, or the like.

According to the embodiments illustrated in Fig. 8, the cutting unit 4 comprises a hub 16 and a number of cutting members 19 pivotally attached at a periphery of the hub 16. Moreover, according to these embodiments, the hub 16 is disc-shaped. The number of cutting members 19 and the hub 16 may comprise the same features, functions, and advantages as the cutting members 19 and the hub 16 explained with reference to Fig. 1 - Fig. 6.

Moreover, according to some embodiments of the herein described, the cutting arrangement 2 illustrated in Fig. 8 may comprise a cutting unit 4 according to the embodiments illustrated in Fig. 7.

The cutting unit 4 of the cutting arrangement 2 is configured to rotate such that one or more radially outer portions 4' of the cutting unit 4 orbits in a circular path C inside the cutting guard 3. As can be clearly seen in Fig. 8, also in these embodiments, the cutting arrangement 2 is arranged such that a first radial distance r1 from the circular path C to an inner surface 5' of a front section 5 of the cutting guard 3 is greater than a second radial distance r2 from the circular path C to an inner surface 6' of a rear section 6 of the cutting guard 3. The first and second radial distances r1, r2 may be defined and measured in the same manner as described with reference to Fig. 3 and Fig. 4 above.

Fig. 9 illustrates a cross section of the cutting arrangement 2 illustrated in Fig. 8. ln Fig. 9, the cross section is made in a plane comprising the rotation axis Ax of the cutting unit 4. ln other words, in Fig. 9, the cross section is made in a plane perpendicular to the rotation plane pr of the cutting unit 4. ln Fig. 9, the first and second radial distances r1, r2 are indicated.

According to the embodiments illustrated in Fig. 8 and Fig. 9, the first radial distance r1 is more than eight times larger than the second radial distance r2. ln more detail, according to the embodiments illustrated in Fig. 8 and Fig. 9, the first radial distance r1 is approximately 810% of the second radial distance r2. According to further embodiments, the first radial 29 distance r1 may be within the range of 150% - 1300% of the second radial distance r2 or may be within the range of 600% - 900% of the second radial distance r2.

As indicated in Fig. 9, also in these embodiments, the cutting unit 4 comprises a number of surfaces 22' being angled relative to a rotation plane Pr of the cutting unit 4 to generate an airflow in a direction d1 transverse to the rotation plane Pr during operation of the cutting unit 4. According to the i||ustrated embodiments, the surfaces 22' are angled relative to the rotation plane Pr to generate an airflow in a direction d1 towards a top surface 13 of the cutting guard 3 during operation of the cutting unit 4. ln this manner, a negative pressure can be generated inside the cutting guard 3 in an efficient manner to further ensure that grass is |ifted towards the cutting unit 4 during operation of the cutting arrangement 2.

However, due to the relatively large distance r1 from the inner surface 5' of the front section 5 and radially outer portions 4' of the cutting arrangement 2, the surfaces 22' can be provided with relatively small angles relative to the rotation plane Pr of the cutting unit 4 while ensuring a satisfactory cutting/mulching result. The one or more surfaces 22' of the cutting unit 4 may be angled relative to the rotation plane Pr of the cutting unit 4 with an angle falling within one of the ranges explained with reference to Fig. 6 above. By using relatively small angles between the one or more surfaces 22' and the rotation plane pr, a low rotational resistance of the cutting unit 4 and hence a low energy consumption of the cutting unit 4 is provided. Moreover, small angles between the one or more surfaces 22' and the rotation plane pr lower air flow in unwanted directions which in turn reduces the rotational resistance of the cutting unit 4 and hence the energy consumption of the cutting arrangement 2.

According to the embodiments i||ustrated in Fig. 9, the cutting arrangement 2 comprises no discharge opening 23. lnstead, inner surfaces 3', 5', 6', 7' of the cutting guard 3 encloses the entire circumference of the cutting unit 4 and also the entire circumference of the of the circular path C. ln Fig. 8, a third radial distance r3 from the circular path C to an inner surface 7' of the side section 7 is indicated. The third radial distance r3 may be defined and measured in the same manner as described with reference to Fig. 3 and Fig. 4 above. As can be seen in Fig. 3, also in these embodiments, the first radial distance r1 is greater than the third radial distance r3. However, in these embodiments, the third radial distance r3 is substantially the same as the second radial distance r2. Since the first radial distance r1 is greater than the third radial distance r3 conditions are provided for forming a negative pressure inside the cutting guard 3 using a low amount of energy.

Moreover, as can be seen in Fig. 8, the radial distance r3, r3', r1 from the Circular path C to an inner surface 7', 3', 5' of cutting guard 3 increases continuously from the side section 7 of the cutting guard 3 towards the front section 5 of the cutting guard 3. Due to these features, conditions are provided for obtaining advantageous aerodynamical properties inside the cutting guard 3 which can reduce the rotationa| resistance of the cutting unit 4 and hence the energy consumption of the cutting unit 4.

According to the i||ustrated embodiments, the radius r of the circu|ar path C is 200 mm. According to further embodiments, the radius r of the circu|ar path C may be within the range of 50 - 400 mm or within the range of 150 - 250 mm. Moreover, according to the i||ustrated embodiments, the length L of the cutting edges 17 of the cutting unit 4 is approximately 58 mm. According to further embodiments, the length L of the cutting edges 17 may be within the range of 20 - 80 mm, or within the range of 35 - 65 mm. Moreover, the length L of the cutting edges 17 may be within the range of 12% - 50% of the radius r of the circu|ar path C or may be within the range of 17% - 33% of the radius r of the circu|ar path C.

Moreover, according to the i||ustrated embodiments, the first radial distance r1 is approximately 57 mm. According to further embodiments, the first radial distance r1 may be within the range of 20 - 95 mm, or may be within the range of 27 - 62 mm. Furthermore, according to the i||ustrated embodiments, the second and third radial distances r2, r3 is approximately 7 mm. According to further embodiments, the second and third radial distances r2, r3 may be within the range of 2 - 14 mm or may be within the range of 4 - 9 mm. ln Fig. 9, a centre axis Ca of the cutting guard 3 is indicated. The centre axis Ca of the cutting guard 3 extends through a centre of the cutting guard 3 in a direction parallel to the rotation axis Ax of the cutting unit 4. As clearly seen in Fig. 9, also in these embodiments, the rotation axis Ax of the cutting unit 4 is displaced relative the centre axis Ca in a direction towards the rear section 6 of the cutting guard 3. ln other words, the rotation axis Ax of the cutting unit 4 is closer to the rear section 6 of the cutting guard 3 than to the centre axis Ca of the cutting guard 3. ln Fig. 9, a motor 31 of the cutting arrangement 2 is indicated. The motor 31 is configured to rotate the cutting unit 4 during operation of the lawnmower 1. The motor 31 may be comprised in a lawnmower 1 comprising the cutting arrangement 2. According to the i||ustrated embodiments, the motor 31 is an electric motor. According to further embodiments, 31 the motor 31 may be another type of motor for rotating the cutting unit 4, such as an internal combustion engine.

According to the illustrated embodiments, the motor 31 is configured to rotate the cutting unit 4 during operation of the lawnmower 1 at a rotational speed causing the one or more radially outer portions 4' of the cutting unit 4 to orbit at a velocity of approximately 70 metres per second. According to further embodiments, the motor 31 may be configured to rotate the cutting unit 4 during operation of the lawnmower 1 at a rotational speed causing the one or more radially outer portions 4' of the cutting unit 4 to orbit at a velocity within the range of 60 - 80 metres per second, or within the range of 65 - 75 metres per second.

The first, second, and third radial distances r1, r2, r3, as referred to herein, may also be referred to as a first, second, or third distance r1, r2, r3 measured in a radial direction rd of the circular path C, measured in a radial direction rd of the cutting unit 4, and/or measured in a radial direction rd of the cutting guard 3. Moreover, the first, second, and third radial distances r1, r2, r3, as referred to herein, may also be referred to as a first, second, or third distance r1, r2, r3 measured in a direction extending through the rotation axis Ax of the cutting unit 4 and being perpendicular to the rotation axis Ax of the cutting unit 4.

The wording “substantially parallel to", as used herein, may encompass that the angle between the objects referred to is less than 10 degrees, or is less than 7 degrees The wording “substantially planar", as used herein, may encompass that the object referred to deviates less than 10% from the shape of a flat plane.

The wording “substantially perpendicular to", as used herein, may encompass that the angle between the objects referred to is within the range of 80 - 100 degrees or is within the range of 83 - 97 degrees.

The wording “substantially the same as", as used herein, may encompass that the aspects, objects, distances, or measurements referred to deviates less than 7% from each other. lt is to be understood that the foregoing is illustrative of various example embodiments and that the invention is defined only by the appended independent claims. A person skilled in the art will realize that the example embodiments may be modified, and that different features of the example embodiments may be combined to create embodiments other than 32 those described herein, without departing from the scope of the present invention, as defined by the appended independent claims.

As used herein, the term "comprising" or "comprises" is open-ended, and includes one or more stated features, elements, steps, components, or functions but does not prec|ude the presence or addition of one or more other features, elements, steps, components, functions, or groups thereof.

Claims (1)

1. CLAIMS A cutting arrangement (2) configured to be attached to a lawnmower (1) to cut vegetation, wherein the cutting arrangement (2) is configured to be attached to the lawnmower (1) such that a forward direction (fd) of the cutting arrangement (2) coincides with a forward direction (fd') of the lawnmower (1), and wherein the cutting arrangement (2) comprises: - a cutting guard (3), and - a cutting unit (4) configured to rotate such that one or more radially outer portions (4') of the cutting unit (4) orbits in a circu|ar path (C) inside the cutting guard (3), wherein the cutting guard (3) comprises a front section (5) and a rear section (6), seen relative to the fonNard direction (fd) of the cutting arrangement (2), together enclosing a portion of the cutting unit (4), and wherein a first radia| distance (r1) from the circu|ar path (C) to an inner surface (5') of the front section (5) of the cutting guard (3) is greater than a second radia| distance (r2) from the circu|ar path (C) to an inner surface (6') of the rear section (6) of the cutting guard (3). _ The cutting arrangement (2) according to c|aim 1, wherein the first radia| distance (r1) is within the range of 150% - 1300% of the second radia| distance (r2) or is within the range of 350% - 900% of the second radia| distance (r2). The cutting arrangement (2) according to c|aim 1 or 2, wherein the cutting guard (3) comprises a side section (7) enclosing a portion of the circu|ar path (C), and wherein the first radia| distance (r1) is greater than a third radia| distance (r3) from the circu|ar path (C) to an inner surface (7') of the side section (7) of the cutting guard (3). _ The cutting arrangement (2) according to c|aim 3, wherein the third radia| distance (r3) is greater than the second radia| distance (r2). The cutting arrangement (2) according to c|aim 3 or 4, wherein the radia| distance (r3, r3', r1) from the circu|ar path (C) to an inner surface (7', 3', 5') of cutting guard (3) increases continuously from the side section (7) of the cutting guard (3) towards the front section (5) of the cutting guard (3). The cutting arrangement (2) according to any one of the preceding claims, wherein the first radia| distance (r1) is within the range of 15 - 80 mm, or is within the range of 25 - 45 mm.The cutting arrangement (2) according to any one of the preceding claims, wherein the second radial distance (r2) is within the range of 2 - 14 mm, or is within the range of 4 - 9 mm. The cutting arrangement (2) according to any one of the preceding claims, wherein the cutting guard (3) comprises a discharge opening (23) arranged to eject clippings in a main discharge direction (dm) being transversal to the forward direction (fd) of the cutting arrangement (2). The cutting arrangement (2) according to c|aim 8, wherein the angle (ad) between the main discharge direction (dm) and the forward direction (fd) is within the range of 30 - 170 degrees or is within the range of 70 - 150 degrees. The cutting arrangement (2) according to c|aim 8 or 9, wherein the width (w) of the discharge opening (23), measured in a rotation plane (Pr) of the cutting unit (4), is within the range of 50% - 150% of the radius (r) of the circular path (C), or is within the range of 108% - 138% of the radius (r) of the circular path (C). The cutting arrangement (2) according to any one of the preceding claims, wherein the cutting unit (4) comprises one or more surfaces (21', 22') being angled relative to a rotation plane (Pr) of the cutting unit (4) to generate an airflow in a direction (d1) transverse to the rotation plane (Pr) during operation of the cutting unit (4). .The cutting arrangement (2) according to c|aim 11, wherein the surfaces (21', 22') are angled relative to the rotation plane (Pr) to generate an airflow in a direction (d1)towards a top surface (13) of the cutting guard (3) during operation of the cutting unit (4). The cutting arrangement (2) according to c|aim 11 or 12, wherein the one or more surfaces (21', 22') is/are angled relative to the rotation plane (Pr) with an angle (a2) within the range of 12 - 38 degrees, or within the range of 17 - 23 degrees. The cutting arrangement (2) according to any one of the preceding claims, wherein the cutting unit (4) comprises a hub (16) and a number of cutting members (19) pivota||y attached at a periphery of the hub (16). 15. A lawnmower (1) comprising a cutting arrangement (2) according to any one of the preceding claims. The lawnmower (1) according to claim 15, wherein the lawnmower (1) is a self-propelled robotic lawnmower (1) configured to navigate and cut grass in an area in an autonomous mannef. The lawnmower (1) according to claim 15 or 16, wherein the lawnmower (1) comprises a motor (31) configured to rotate the cutting unit (4) during operation of the lawnmower (1) at a rotational speed causing the one or more radially outer portions (4') of the cutting unit (4) to orbit at a velocity within the range of 60 - 80 metres per second, or within the range of 65 - 75 metres per second.