Patent Description:
Various types of lawnmowers exist on today's market. Examples are walk-behind mowers, riding 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". A riding mower is a mower comprising a seat for a user, a steering device, such as a steering wheel, and a motor configured to provide motive power to the riding mower. Usually, riding mowers are used to mow bigger lawns, gardens, parks, sports fields, golf courts or the like.

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. In 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. In 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.

The above-mentioned types of lawnmowers use a cutting deck to cut grass. Traditionally, a cutting deck comprises a cutting device in the form of an elongated cutting arm which is rotated horizontally over a ground surface. As cutting portions of the elongates cutting arm hits vegetation, the vegetation is being cut.

Some lawnmowers comprise an electric motor configured to rotate the cutting device and some lawnmowers comprise a combustion engine configured to rotate the cutting device. The use of an electric motor provides several advantages over the use of a combustion engine when it comes to emission levels, noise levels, operational reliability, and the need for service and repair. However, a problem associated with electrically powered lawnmowers is available operational time. That is, in riding mowers and self-propelled robotic lawnmowers it is usually not practically possible to use a power cord to power the electric motor. Therefore, these types of lawnmowers usually comprise one or more batteries configured to power the electric motor. When such one or more batteries are emptied, they must be recharged or replaced. One solution to prolong the available operational time could be to increase the size and/or the number of batteries. However, such a solution adds weight and costs to the lawnmower and in many cases, these is a practical limit for the size of the batteries of a lawnmower.

Available operational time is also a problem for lawnmowers comprising a combustion engine. This because such lawnmowers comprise a tank accommodating fuel, and when such a tank is emptied, it must be replenished.

Furthermore, various types of lawnmowers, such as those described above, are associated with some mutual problems. One such problem is 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.

The document <CIT> relates to a lawn mower of the cross-flow blower type, employing a cylindrical reel with circumferentially-spaced cutting blades in a blower conduit having upper and lower wall sections with respective portions close to the reel at circumferentially spaced positions separating inlet and outlet regions of the blower. A curved forward extension of the upper wall section is provided which extends forwardly to the portion thereof close to the reel, the lower surface of the extension being concave in cross-section and designed to produce a vortex there beneath which rotates in a direction opposite to the direction of rotation of the reel.

The document <CIT> relates to a lawn mower in which a cutting cylinder is supported at its ends between two laterally spaced flanges one of which extends further forwardly than the other.

The document <CIT> relates to a reel type lawn mower comprising a frame of cast aluminium including a pair of end plates and a tubular portion extending between said end plates and rigidly connected thereto. A steel tube is housed within the tubular portion with the ends thereof embedded in the end plates. A pair of members is seated against the ends of said tube and held against rotation relative to said frame. A tension bolt extends through the tube and bearing against the outer sides of said members, the ends of said tension bolt being eccentrically disposed relative to the axis of said tube, and a lug in said tube is forced by said tension bolt against the central portion of said tube.

The document <CIT> relates to an apparatus for removing weed growth from an irrigation ditch of generally V-shaped contour. The apparatus is caused to ride within the ditch while being towed by a vehicle. The apparatus has two motor-driven mowing axles adapted to be adjustably disposed upon the opposite walls of the ditch. Each axle has a multitude of flail-type cutting blades. The axles are preferably rotated in opposite directions.

According to an aspect of the invention, the object is achieved by a lawnmower cutting deck, wherein the cutting deck is configured to be moved in a forward direction over a ground surface to cut grass. The cutting deck comprises at least a first cutter shaft and at least one cutting unit arranged on the first cutter shaft. The first cutter shaft is configured to rotate around a first rotational axis extending substantially parallel to the ground surface to rotate the at least one cutting unit in a first rotational plane. The first rotational plane is angled in relation to the forward direction.

Thereby, a cutting deck is provided capable of cutting grass in an energy efficient manner. This because the first cutter shaft is configured to rotate around the first rotational axis extending substantially parallel to the ground surface to rotate the at least one cutting unit in the first rotational plane. As a result thereof, when cutting portions of the at least one cutting unit hits vegetation, such as a grass straw, such a grass straw is being cut in a direction causing a more beneficial opposing force in the grass straw, via the root of the grass straw, as compared to when a cutting device rotating in a horizontal plane hits vegetation. Therefore, a cutting deck is provided capable of cutting grass in a manner causing a lower resistance torque in the cutter shaft. Accordingly, the cutting deck is capable of cutting grass using a low amount of energy.

As a further result thereof, a cutting deck is provided capable of increasing an available operational time of a lawnmower comprising the cutting deck. Furthermore, a more environmentally friendly cutting deck is provided.

Further, since the first rotational plane is angled in relation to the forward direction, the area covered by the at least one cutting unit, during movement of the cutting deck in the forward direction, is increased. Thereby, the efficiency of the cutting is improved, and the cutting result can be improved.

Still further, a cutting deck is provided capable of cutting clippings into small pieces, thus providing a mulched cutting result, while using a low amount of energy. In addition, a cutting deck is provided having conditions for distributing the clippings uniformly back into a lawn.

The first rotational plane is angled in relation to the forward direction at a first angle, and wherein the first angle is within the range of <NUM> degrees to degrees <NUM>, or within the range of <NUM> degrees to <NUM> degrees. Thereby, an efficient cutting is provided, while a proper cutting result is ensured, because the at least one cutting unit covers a significant area during movement of the cutting deck in the forward direction.

The cutting deck comprises a second cutter shaft and at least one cutting unit arranged on the second cutter shaft, wherein the second cutter shaft is configured to rotate around a second rotational axis extending substantially parallel to the ground surface to rotate the at least one cutting unit in a second rotational plane, and wherein the second rotational plane is angled in relation to the forward direction. Thereby, the efficiency of the cutting is improved because the cutting units of the first and second cutter shafts together cover a great area during movement of the cutting deck in the forward direction. As a further result thereof, the cutting result is improved.

The second rotational plane is angled in relation to the forward direction at a second angle, and wherein the second angle is within the range of <NUM> degrees to degrees <NUM>, or within the range of <NUM> degrees to <NUM> degrees. Thereby, an efficient cutting is provided, while a proper cutting result is ensured, because the at least one cutting unit of the second cutter shaft covers a significant area during movement of the cutting deck in the forward direction.

The second angle is different from the first angle. Thereby, the cutting result and the efficiency of cutting can be further improved because cutting units of the second cutter shaft will have a different cutting angle than cutting units of the first cutter shaft.

The second cutter shaft is arranged behind the first cutter shaft seen in the forward direction. Thereby, the cutting result is further improved. This because cutting units of the second shaft may cut grass that has not been cut by cutting units of the first shaft.

Accordingly, a lawnmower cutting deck 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 at least one cutting unit comprises a rotor and one or more cutting members arranged on the rotor at a distance from the first rotational axis. Thereby, an efficient cutting is provided.

Optionally, each cutting member is pivotably arranged on the rotor. Thereby, an efficient cutting is provided, while safety during operation of the cutting deck is improved. This because if a cutting member is hitting for example a limb of a user, the cutting member may pivot instead of causing injury to the limb. Still further, the operational reliability of the cutting deck is improved. This because if a cutting member is hitting a hard object, such as a stone, it may pivot instead of getting damaged.

Optionally, each cutting member is pivotably arranged about a respective pivot axis, and wherein each pivot axis is substantially perpendicular to the first rotational plane. Thereby, an efficient cutting is provided, while safety during operation of the cutting deck is further improved. This because if a cutting member is hitting for example a limb of a user, the cutting member may pivot in a plane parallel to the first rotational plane instead of causing injury to the limb. Still further, the operational reliability of the cutting deck is further improved. This because if a cutting member is hitting a hard object, such as a stone, it may pivot in a plane parallel to the first rotational plane instead of getting damaged.

Optionally, each cutting member comprises a cutting edge extending in a direction substantially parallel to the first rotational plane. Thereby, a low resistance in the first cutter shaft is provided upon rotation of the at least one cutting unit. As a result, an energy efficient cutting deck is provided. Further, a cutting deck is provided capable of cutting clippings into small pieces, thus providing a mulched cutting result, while using a low amount of energy.

Optionally, each cutting member comprises a cutting portion extending in the first rotational plane. Thereby, a low resistance in the first cutter shaft is provided upon rotation of the at least one cutting unit. As a result, an energy efficient cutting deck is provided. Further, a cutting deck is provided capable of cutting clippings into small pieces, thus providing a mulched cutting result, while using a low amount of energy.

Optionally, the rotor is disc-shaped. Thereby, a low resistance in the first cutter shaft is provided upon rotation of the at least one cutting unit. As a result, an energy efficient cutting deck is provided. In addition, the safety during operation of the cutting deck is further improved. This because if the rotor is hitting for example a limb of a user, the rotor is less likely to cause injury to the limb than would be the case if the rotor had another type of shape. Further, the operational reliability of the cutting deck is further improved. This because if the rotor is hitting a hard object, such as a stone, the rotor is less likely to become damaged than if the rotor had another type of shape.

Optionally, the cutting deck is arranged such that a kinetic energy of each cutting member is below <NUM> Joules, or is below <NUM> Joules, during operation of the cutting deck. Thereby, an efficient cutting is provided, while safety during operation of the cutting deck is further ensured.

Optionally, the at least one cutting unit comprises a lower portion between the first rotational axis and the ground surface, and an upper portion above the first rotational axis, and wherein the cutting deck comprises a cover covering the upper portion of the at least one cutting unit. Thereby, a safer cutting deck is provided. In addition, the visual cutting result can be improved because the cover may guide grass being cut along an inner surface thereof. As a further result, a cutting deck is provided having conditions for further efficient distribution of clippings back into a lawn.

Optionally, the cutting deck comprises at least one guiding member arranged adjacent to the first rotational plane, and wherein the at least one guiding member is configured to guide grass towards the first rotational plane during operation of the cutting deck. Thereby, a further efficient cutting is provided, because the guiding member is configured to guide grass towards the first rotational plane in which the at least one cutting unit is rotating.

Optionally, radially outer portions of the at least one cutting unit follow a circular path upon rotation of the at least one cutting unit, and wherein the guiding member extends in a direction substantially parallel to the first rotational plane to a position adjacent to a lower tangent of the circular path. Thereby, a further efficient cutting is provided, because the guiding member will guide grass towards the first rotational plane in which the at least one cutting unit is rotating. Still further, the operational reliability of the cutting deck is further improved. This because during operation of the cutting deck, the guiding member may bump into an object on the ground surface, such as a stone or stump, instead of the cutting unit. Thereby, the at least one cutting unit can be protected from becoming damaged.

Optionally, the first cutter shaft is configured to rotate in a rotational direction causing a portion of the at least one cutting unit below the first rotational axis to move in a tangential direction having a component in the forward direction. Thereby, a further efficient cutting is provided. This because when cutting portions of the at least one cutting unit hits vegetation, such as a grass straw, such a grass straw is being cut in a forward/upward motion causing a further beneficial opposing force in the grass straw, via the root of the grass straw. Further, the visual cutting result can be improved because grass being cut by the cutting unit may be thrown around the first rotational axis and may be thrown off the cutting unit at a location behind the cutting unit, seen in the forward direction. Thus, cutting deck is provided having conditions for further efficient distribution of clippings back into a law.

Optionally, the cutting deck comprises two or more cutting units arranged at an axial distance from each other along the first cutter shaft. Thereby, the efficiency of the cutting is improved because the two or more cutting units together cover a great area when the cutting deck is moved in the forward direction.

Optionally, one of the first and second rotational planes is angled clockwise in relation to the forward direction seen in a direction towards the ground surface, and the other of the first and second rotational planes, is angled counter clockwise in relation to the forward direction seen in the direction towards the ground surface. Thereby, the cutting result and the efficiency of cutting can be further improved.

Optionally, the cutting deck comprises two or more cutting units arranged on the first cutter shaft and two or more cutting units arranged on the second cutter shaft. Thereby, the cutting result and the efficiency of cutting is further improved. This because cutting units of the first and second cutter shaft together cover a great area when the cutting deck is moved in the forward direction and cutting units of the second cutter shaft may cut grass that has not been cut by cutting units of the first cutter shaft.

Optionally, cutting units of the second cutter shaft are displaced in a direction perpendicular to the forward direction in relation to cutting units of the first cutter shaft approximately half the distance between cutting units of the first cutter shaft measured in the direction perpendicular to the forward direction. Thereby, the cutting result and the efficiency of cutting is further improved. This because cutting units of the first and second cutter shaft together cover a great area when the cutting deck is moved in the forward direction and cutting units of the second cutter shaft may cut grass that has not been cut by cutting units of the first cutter shaft. As a result, the visual cutting result as well as the uniformity of cutting is improved.

Optionally, the cutting deck comprises a third cutter shaft and at least one cutting unit arranged on the third cutter shaft, wherein the third cutter shaft is configured to rotate around a third rotational axis extending substantially parallel to the ground surface to rotate the at least one cutting unit in a third rotational plane, and wherein the third rotational plane is angled in relation to the forward direction. Thereby, the efficiency of the cutting is improved because the cutting unit of the first and third cutter shafts together cover a great area during movement of the cutting deck in the forward direction. As a further result thereof, the cutting result is improved.

Optionally, the third rotational plane is angled in relation to the forward direction at a third angle, and wherein the third angle is within the range of <NUM> degrees to degrees <NUM>, or within the range of <NUM> degrees to <NUM> degrees. Thereby, an efficient cutting is provided, while a proper cutting result is ensured, because the at least one cutting unit of the third cutter shaft covers a significant area during movement of the cutting deck in the forward direction.

Optionally, the third angle is different from the first angle. Thereby, the cutting result and the efficiency of cutting can be further improved because cutting units of the third cutter shaft will have a different cutting angle than cutting units of the first cutter shaft.

Optionally, one of the first and third rotational planes is angled clockwise in relation to the forward direction seen in a direction towards the ground surface, and the other of the first and third rotational planes, is angled counter clockwise in relation to the forward direction seen in the direction towards the ground surface. Thereby, the cutting result and the efficiency of cutting can be further improved.

Optionally, the third cutter shaft is laterally displaced relative the first cutter shaft seen in the forward direction. Thereby, the efficiency of cutting is further improved because cutting units of the first and third cutter shafts together cover a great area upon movement of the cutting deck in the forward direction.

Optionally, the third rotational plane is substantially parallel to the second rotational plane. Thereby, the cutting result is improved because cutting units of the third and second cutter shafts will cut grass in a substantially uniform manner.

Optionally, the cutting deck comprises two or more cutting units arranged on the first cutter shaft and two or more cutting units arranged on the third cutter shaft, and wherein a distance between a point in which the third rotational axis intersects a third rotational plane of a cutting unit of the third cutter shaft and a point in which the first rotational axis intersects a first rotational plane of a cutting unit of the first cutter shaft measured in a direction perpendicular to the forward direction, substantially corresponds to a distance between first rotational planes of cutting units of the first cutter shaft measured in the direction perpendicular to the forward direction. Thereby, the cutting result is further improved because the cutting units are arranged at a substantial equal distance from each other, measured in the direction perpendicular to the forward direction.

Optionally, the cutting deck comprises a fourth cutter shaft and at least one cutting unit arranged on the fourth cutter shaft, wherein the fourth cutter shaft is configured to rotate around a fourth rotational axis extending substantially parallel to the ground surface to rotate the at least one cutting unit in a fourth rotational plane, and wherein the fourth rotational plane is angled in relation to the forward direction. Thereby, the efficiency of the cutting is improved because the cutting unit of the first and fourth cutter shafts together cover a great area during movement of the cutting deck in the forward direction. As a further result thereof, the cutting result is improved.

Optionally, the fourth rotational plane is angled in relation to the forward direction at a fourth angle, and wherein the fourth angle is within the range of <NUM> degrees to degrees <NUM>, or within the range of <NUM> degrees to <NUM> degrees. Thereby, an efficient cutting is provided, while a proper cutting result is ensured, because the at least one cutting unit of the fourth cutter shaft covers a significant area during movement of the cutting deck in the forward direction.

Optionally, the fourth angle is different from the third angle. Thereby, the cutting result and the efficiency of cutting can be further improved because cutting units of the fourth cutter shaft will have a different cutting angle than cutting units of the third cutter shaft.

Optionally, one of the third and fourth rotational planes is angled clockwise in relation to the forward direction seen in a direction towards the ground surface, and the other of the third and fourth rotational planes, is angled counter clockwise in relation to the forward direction seen in the direction towards the ground surface. Thereby, the cutting result and the efficiency of cutting can be further improved.

Optionally, the fourth cutter shaft is arranged behind the third cutter shaft seen in the forward direction. Thereby, the cutting result is further improved. This because cutting units of the fourth cutter shaft may cut grass which not is cut by cutting units of the third cutter shaft.

Optionally, the fourth rotational plane is substantially parallel to the first rotational plane. Thereby, the cutting result is improved because cutting units of the fourth and first cutter shafts will cut grass in a substantially uniform manner.

Optionally, the cutting deck comprises two or more cutting units arranged on the third cutter shaft and two or more cutting units arranged on the fourth cutter shaft. Thereby, the cutting result and the efficiency of cutting is further improved. This because cutting units of the third and fourth cutter shaft together cover a great area when the cutting deck is moved in the forward direction and cutting units of the fourth cutter shaft may cut grass which not is cut by cutting units of the first cutter shaft.

Optionally, cutting units of the fourth cutter shaft are displaced in a direction perpendicular to the forward direction in relation to cutting units of the third cutter shaft approximately half the distance between cutting units of the third cutter shaft measured in the direction perpendicular to the forward direction. Thereby, the cutting result and the efficiency of cutting is further improved. This because cutting units of the third and fourth cutter shaft together cover a great area when the cutting deck is moved in the forward direction and cutting units of the fourth cutter shaft may cut grass that has not been cut by cutting units of the third cutter shaft. As a result, the visual cutting result as well as the uniformity of cutting is improved.

Optionally, the cutting deck comprises two or more cutting units arranged on the second cutter shaft and two or more cutting units arranged on the fourth cutter shaft, and wherein a distance between a point in which the fourth rotational axis intersects a fourth rotational plane of a cutting unit of the fourth cutter shaft and a point in which the second rotational axis intersects a second rotational plane of a cutting unit of the second cutter shaft measured in a direction perpendicular to the forward direction, substantially corresponds to a distance between second rotational planes of cutting units of the second cutter shaft measured in the direction perpendicular to the forward direction. Thereby, the cutting result is further improved because cutting units are arranged at a substantial equal distance from each other, measured in the direction perpendicular to the forward direction.

Optionally, the first, the second, the third, and the fourth rotational axes, together form a rhomboid. Thereby, the cutting result and the efficiency of cutting is further improved.

Optionally, the number of cutting units arranged on each cutter shaft, of the cutting deck is within the range of three to twenty, or within the range of four to twelve. Thereby, the cutting result and the efficiency of cutting is further improved.

Optionally, the cutting deck comprises a housing covering upper portions of all cutting units of the cutting deck. Thereby, the safety is improved during operation of the cutting deck. This because the risk that an object, such as a limb of a user, is bumping into one or more cutting \units is reduced.

A lawnmower comprising a lawnmower cutting deck according to some embodiments can be capable of cutting grass in an energy efficient manner. This because the cutting deck of the lawnmower comprises at least a first cutter shaft configured to rotate around a first rotational axis extending substantially parallel to the ground surface to rotate at least one cutting unit in a first rotational plane. As a result thereof, when cutting portions of the at least one cutting unit hits vegetation, such as a grass straw, such a grass straw is being cut in a direction causing a more beneficial opposing force in the grass straw, via the root of the grass straw, as compared to when a cutting device rotating in a horizontal plane hits vegetation. Therefore, a lawnmower is provided capable of cutting grass in a manner causing a lower resistance torque in the cutter shaft. Accordingly, the lawnmower is capable of cutting grass using a low amount of energy.

As a further result thereof, a lawnmower is provided having conditions for a prolonged operational time. Further, a more environmentally friendly lawnmower can be provided.

Furthermore, since the first rotational plane is angled in relation to the forward direction, the area covered by the at least one cutting unit, during movement of the lawnmower in the forward direction, is increased. Thereby, the efficiency of the cutting is improved, and the cutting result can be improved.

Still further, a lawnmower can be provided capable of cutting clippings into small pieces, thus providing a mulched cutting result, while using a low amount of energy. In addition, a lawnmower can be provided having conditions for distributing the clippings uniformly back into a lawn.

Optionally, the lawnmower comprises an electric motor configured to rotate one or more cutter shafts of the lawnmower. Thereby, an environmentally friendly lawnmower is provided having conditions for generating low noise levels during operation and low emission levels during operation. Still further, a lawnmower is provided having conditions for an increased available operational time because the lawnmower comprises an energy efficient cutting deck.

Optionally, the lawnmower comprises one electric motor per cutter shaft, and wherein each electric motor is configured to rotate a respective cutter shaft. Thereby, an efficient, simple, and reliable rotation of cutter shafts is provided.

Optionally, the lawnmower is a self-propelled robotic lawnmower. Thereby, a self-propelled robotic lawnmower is provided having conditions for an increased available operational time because the self-propelled robotic lawnmower comprises an energy efficient cutting deck. Further, an environmentally friendly self-propelled robotic lawnmower can be provided having conditions for generating low noise levels during operation and low emission levels during operation. Still further, a self-propelled robotic lawnmower is provided capable of cutting clippings into small pieces, thus providing a mulched cutting result, while using a low amount of energy. In addition, a self-propelled robotic lawnmower is provided having conditions for distributing the clippings uniformly back into a lawn.

Optionally, the lawnmower is a riding mower comprising a seat for an operator. Thereby, a riding mower is provided having conditions for an increased available operational time because the riding mower comprises an energy efficient cutting deck. Further, an environmentally friendly riding mower can be provided having conditions for generating low noise levels during operation and low emission levels during operation. Still further, a riding mower is provided capable of cutting clippings into small pieces, thus providing a mulched cutting result, while using a low amount of energy. In addition, a riding mower is provided having conditions for distributing the clippings uniformly back into a lawn.

<FIG> illustrates a lawnmower cutting deck <NUM>, according to some embodiments. For the reason of brevity, the lawnmower cutting deck <NUM> is in some places herein referred to as the cutting deck <NUM>. In <FIG>, the cutting deck <NUM> is illustrated as being viewed from above when the cutting deck <NUM> is positioned on a ground surface <NUM>. The cutting deck <NUM> is configured to be moved in a forward direction d1 over a ground surface <NUM> to cut grass. The cutting deck <NUM> comprises at least a first cutter shaft <NUM> and at least one cutting unit <NUM> arranged on the first cutter shaft <NUM>. According to the illustrated embodiments, the cutting deck <NUM> comprises four cutter shafts <NUM>, <NUM>, <NUM>, <NUM> each comprising eight cutting units <NUM> arranged on the respective cutter shaft <NUM>, <NUM>, <NUM>, <NUM>. Herein, these cutter shafts <NUM>, <NUM>, <NUM>, <NUM> are referred to as the first cutter shaft <NUM>, the second cutter shaft <NUM>, the third cutter shaft <NUM>, and the fourth cutter shaft <NUM>. However, as will be further explained herein the cutting deck <NUM> may comprise another number of cutter shafts <NUM>, <NUM>, <NUM>, <NUM> which may each comprise another number of cutting units <NUM> than eight. However, for the reason of brevity, in the following section below, reference is made to the first cutter shaft <NUM> of the four cutter shafts <NUM>, <NUM>, <NUM>, <NUM>.

The first cutter shaft <NUM> is configured to rotate around a first rotational axis ax1. When the cutting deck <NUM> is positioned onto a ground surface <NUM>, the first rotational axis ax1 extends substantially parallel to the ground surface <NUM>. The feature that the first rotational axis ax1 extends substantially parallel to the ground surface <NUM> may encompass that an angle between the first rotational axis ax1 and the ground surface <NUM> is less than <NUM> degrees. The cutting units <NUM> of the first cutter shaft <NUM> are arranged on the first cutter shaft <NUM>. When the first cutter shaft <NUM> is rotating around the first rotational axis ax1, each cutting unit <NUM> of the first cutter shaft <NUM> is rotating in a respective first rotational plane p1. For the reason of brevity, one such first rotational plane p1 is indicated with the reference sign "p1" in <FIG>. The cutting units <NUM> of the first cutter shaft <NUM> are arranged at an axial distance d from each other along the first cutter shaft <NUM>. Since the cutting units <NUM> are arranged on the first rotational axis ax1 and since the first cutter shaft <NUM> is arranged to rotate around the first rotational axis ax1 being substantially parallel to the ground surface <NUM>, each first rotational plane p1 is substantially perpendicular to the ground surface <NUM>. Further, as can be seen in <FIG>, the first rotational plane p1 is angled in relation to the forward direction d1. Due to these features, a cutting deck <NUM> is provided capable of cutting grass in an efficient manner requiring a low amount of energy.

The first rotational plane p1 is angled in relation to the forward direction d1 at a first angle a1. According to the illustrated embodiments, the first angle a1 is approximately <NUM> degrees. According to further embodiments, the first angle a1 may be within the range of <NUM> degrees to <NUM> degrees, or within the range of <NUM> degrees to <NUM> degrees, or within the range of <NUM> degrees to <NUM> degrees.

The second cutter shaft <NUM> of the cutting deck <NUM> is arranged behind the first cutter shaft <NUM> seen in the forward direction d1.

<FIG> illustrates a cross section of the lawnmower cutting deck <NUM> illustrated in <FIG>. In the cross section of <FIG>, the cutting deck <NUM> is illustrated as being viewed from the side, i.e. in a direction parallel to the ground surface <NUM> and perpendicular to the forward direction d1. In <FIG>, one cutting unit <NUM> of the first cutter shaft <NUM> and one cutting unit <NUM> of the second cutter shaft <NUM> are visible. Below, some features and advantages are explained with reference to the cutting unit <NUM> of the first cutter shaft <NUM>, and some features and advantages are explained with reference to the cutting unit <NUM> of the second cutter shaft <NUM>. However, according to the illustrated embodiments, all cutter shafts <NUM>, <NUM>, <NUM>, <NUM> of the cutting deck <NUM> comprises the same type of cutting units <NUM> comprising the same features and advantages. Accordingly, features and advantages explained herein with reference a cutting unit <NUM> of one cutter shaft <NUM>, <NUM>, <NUM>, <NUM> are applicable to cutting units <NUM> of other cutter shaft <NUM>, <NUM>, <NUM>, <NUM> of the cutting deck <NUM>.

As indicated in <FIG>, the cutting unit <NUM> comprises a rotor <NUM> and one or more cutting members <NUM> arranged on the rotor <NUM> at a distance from the first rotational axis ax1. According to the illustrated embodiments, three cutting members <NUM> are arranged each rotor <NUM>. According to further embodiments, each rotor <NUM> may comprise another number of cutting members <NUM>, such as one, two, four, five, or six. According to the illustrated embodiments, each cutting member <NUM> is attached to the rotor <NUM>. According to some embodiments, each cutting member <NUM> may be removably attached to the rotor <NUM>. Each cutting member <NUM> is pivotably arranged on the rotor <NUM> about a respective pivot axis <NUM>. Each pivot axis <NUM> is substantially perpendicular to the rotational plane of the cutting unit <NUM>. According to the illustrated embodiments, the rotor <NUM> is disc-shaped and each pivot axis <NUM> is arranged at a distance from a radially outer edge <NUM>' of the disc-shaped rotor <NUM>. The radially outer edge <NUM>' of the disc-shaped rotor <NUM> is substantially circular. Each cutting member <NUM> is provided with a length being greater than the distance between the pivot axis <NUM> and the radially outer edge <NUM>' of the disc-shaped rotor <NUM>. Further, each cutting member <NUM> is configured to assume a radial position by centrifugal force acting on the cutting member <NUM> during rotation of the cutting unit <NUM>, causing the cutting member <NUM> to extend past the radially outer edge <NUM>' of the rotor <NUM>.

Each cutting member <NUM> comprises a cutting edge <NUM> extending in a direction <NUM> substantially parallel to the rotational plane of the cutting unit <NUM>. Further, each cutting member <NUM> comprises a cutting portion <NUM> extending in the rotational plane of the cutting unit <NUM>. Due to these features, an energy efficient cutting can be performed because the cutting units <NUM> are subjected to a low amount of resistance during cutting, as well as a low amount of air resistance during rotation of the cutting unit <NUM>. In addition, since the cutting members <NUM> are pivotably arranged on the rotor <NUM> about a respective pivot axis <NUM>, the cutting members <NUM> may pivot in case cutting members <NUM> strikes a hard object, or a limb of a user. In this manner, the safety during operation of the cutting deck <NUM> is improved, as well as the operational reliability of the cutting deck <NUM>.

According to the illustrated embodiments, the cutter shafts <NUM>, <NUM> of the cutting deck <NUM> are each configured to rotate in a respective rotational direction causing a respective portion <NUM> of cutting units <NUM>, below the rotational axis ax1, ax2 of the cutter shaft <NUM>, <NUM> to move in a tangential direction having a component in the forward direction d1.

<FIG> schematically illustrates the portion <NUM> of the cutting unit <NUM> of the first cutter shaft <NUM>, illustrated in <FIG>. Further, in <FIG>, the forward direction d1 is illustrated as well as a direction d2 perpendicular to the forward direction d1. As can be seen in <FIG>, the portion <NUM> of the cutting unit will move in a tangential direction <NUM> having a component <NUM> in the forward direction d1 during rotation of the first cutter shaft. Since the first rotational plane of the cutting unit is angled in relation to the forward direction d1 at the angle a1, the portion <NUM> of the cutting unit will move in a tangential direction <NUM> having a component <NUM> in the forward direction d1, during rotation of the first cutter shaft, as well as a component <NUM>' in the direction d2 perpendicular to the forward direction d1.

Below, reference is made to <FIG>, as well as to <FIG>. According to the illustrated embodiments, portions <NUM> of cutting units <NUM> below the respective rotational axis ax1, ax2, ax3, ax4 move in directions having components in the forward direction d1. As a result, an efficient cutting is achieved and a cutting deck <NUM> is provided capable of cutting clippings into small pieces, thus providing a mulched cutting result, while using a low amount of energy. This because when the cutting deck <NUM> is moved in the forward direction <NUM>, the cutting will be performed in a forward/upward motion by the cutting members <NUM>, which is advantageous regarding the energy consumption as well as regarding the cutting result. One reason is that a more beneficial opposing force in a grass straw, via the root of the grass straw, is obtained because the cutting is performed in a forward/upward motion.

As indicated in <FIG>, the cutting unit <NUM> of the first cutter shaft <NUM> comprises a lower portion <NUM> between the first rotational axis ax1 and the ground surface <NUM>, and an upper portion <NUM> above the first rotational axis ax1, when the cutting deck <NUM> is positioned onto a ground surface <NUM> in an intended operational position. The cutting deck <NUM> comprises a cover <NUM> covering the upper portion <NUM> of the cutting unit <NUM>. The cutting deck <NUM> may comprise one cover <NUM> per cutting unit <NUM>, covering the upper portion <NUM> of the respective cutting unit <NUM>. According to further embodiments, the cutting deck <NUM> may comprise one elongated cover per cutter shaft <NUM>, <NUM>, <NUM>, <NUM> covering upper portions <NUM> of cutting units <NUM> of the respective cutter shaft <NUM>, <NUM>, <NUM>, <NUM>.

As indicated in <FIG>, radially outer portions <NUM> of a cutting unit <NUM> follow a circular path <NUM>' upon rotation of the cutting unit <NUM>. According to illustrated embodiments, an inner surface <NUM>' of the cover <NUM> substantially follows the circular path <NUM>'. As a result thereof, during operation of the cutting deck <NUM>, grass being cut by a cutting member <NUM> in the forward/upward motion as explained above, may follow the inner surface <NUM>' of the cover <NUM>, and may be thrown out of the cover <NUM> behind the cutting unit <NUM> seen in the forward direction d1. Thereby, the visual cutting result can be improved and the operational reliability of the cutting deck <NUM> can be further improved. In addition, a cutting deck <NUM> is provided having conditions for distributing the clippings uniformly back into a lawn. Furthermore, due to the covers <NUM>, the safety during operation of the cutting deck <NUM> can be improved.

According to the illustrated embodiments, the cutting deck <NUM> comprises guiding members <NUM> arranged adjacent to rotational planes of cutting members <NUM>. The guiding members <NUM> are configured to guide grass towards the rotational planes of the cutting members <NUM> during operation of the cutting deck <NUM>. As mentioned above, radially outer portions <NUM> of cutting units <NUM> follow a circular path <NUM>' upon rotation of the cutting units <NUM>. According to the illustrated embodiments, the guiding members <NUM> extend in a direction substantially parallel to the rotational plane of the cutting unit <NUM> to a position adjacent to a lower tangent t of the circular path <NUM>'. The lower tangent t is a point of the circular path <NUM>' closest to the ground surface <NUM> when the cutting deck <NUM> is positioned onto a ground surface <NUM> in an intended operational position. Due to these features, a further efficient cutting is provided, because the guiding member <NUM> will guide grass towards the rotational plane in which the cutting unit <NUM> is rotating. In addition, the guiding members <NUM> may ensure that a distance is obtained between rotors <NUM> of the cutting units <NUM> and a ground surface <NUM>, for example also when the cutting deck <NUM> is moved over an uneven ground surface <NUM>. Still further, one or more of the guiding members <NUM> may bump into an object on the ground surface <NUM>, such as a stone or stump, instead of one or more cutting units <NUM>. As a result thereof, the operational reliability of the cutting deck <NUM> can be further improved.

According to some embodiments, the cutting deck <NUM> is arranged such that a kinetic energy of each cutting member <NUM> is below <NUM> Joules, or is below <NUM> Joules, during operation of the cutting deck <NUM>. According to further embodiments, the cutting deck <NUM> is arranged such that a kinetic energy of each cutting member <NUM> is within the range of <NUM> Joules and <NUM> Joules. According to still further embodiments, the cutting deck <NUM> is arranged such that a kinetic energy of each cutting member <NUM> is within the range of <NUM> Joules and <NUM> joules, or is within the range of <NUM> Joules and <NUM> joules, or is within the range of <NUM> Joules and <NUM> joules.

<FIG> schematically illustrates a rotor <NUM> and a cutting member <NUM> of a cutting unit <NUM> according to some embodiments. The kinetic energy of each cutting member <NUM> of a cutting unit <NUM> as described herein may be determined by means of the following formula: <MAT> where.

According to some embodiments of the cutting deck, the distance r from the rotational axis ax of the cutting unit <NUM> to the radially outer portion <NUM> of a cutting member <NUM> is within the range of <NUM> to <NUM>, or is within the range of <NUM> to <NUM>. According to the embodiments illustrated in <FIG>, the distance r is approximately <NUM>.

According to some embodiments of the cutting deck, the reckonable length L of the cutting member <NUM> is within the range of <NUM> to <NUM>, or is within the range of <NUM> to <NUM>. According to the embodiments illustrated in <FIG>, the reckonable length of the cutting member <NUM> is approximately <NUM>.

According to some embodiments of the cutting deck, the mass m, of reckonable length L of the cutting member <NUM>, is within the range of <NUM> to <NUM> grams, or is within the range of <NUM> to <NUM> grams. According to the embodiments illustrated in <FIG>, the mass m, of reckonable length L of the cutting member <NUM>, is approximately <NUM> grams.

According to some embodiments, the thickness of the cutting member <NUM>, i.e. the thickness of the cutting member <NUM> measured in a direction perpendicular to the rotational plane of the cutting member <NUM>, is within the range of <NUM> to <NUM>, or is within the range of <NUM> to <NUM>. According to the embodiments illustrated in <FIG>, the thickness of the cutting member <NUM> of the cutting deck, i.e. the thickness of the cutting member <NUM> measured in a direction perpendicular to the rotational plane of the cutting member <NUM>, is approximately <NUM>.

According to some embodiments, the height h of the cutting member <NUM> of the cutting deck is within the range of <NUM> to <NUM>, or is within the range of <NUM> to <NUM>. According to the embodiments illustrated in <FIG>, the height of the cutting member <NUM> is approximately <NUM>.

According to some embodiments of the cutting deck, the diameter of the rotors <NUM> of the cutting deck is within the range of <NUM> to <NUM>, or is within the range of <NUM> to <NUM>. According to the embodiments illustrated in <FIG>, the diameter of the rotors <NUM> of the cutting deck is approximately <NUM>.

According to some embodiments, the maximum attainable velocity v of the point z which is half way along the reckonable length L of the cutting member <NUM> is within the range of <NUM> to <NUM> metres per second, or is within the range of <NUM> to <NUM> metres per second. According to the embodiments illustrated in <FIG>, the maximum attainable velocity v of the point z which is half way along the reckonable length L of the cutting member <NUM> is approximately <NUM> metres per second.

According to some embodiments, the maximum rotational speed of the cutting unit <NUM> is within the range of <NUM><NUM> to <NUM><NUM> revolutions per minute, or is within the range of <NUM><NUM> to <NUM><NUM> revolutions per minute. According to the embodiments illustrated in <FIG>, the maximum rotational speed of the cutting unit <NUM> is approximately <NUM><NUM> revolutions per minute.

In the following, reference is made to <FIG>. As mentioned above, the cutting deck <NUM> comprises a second cutter shaft <NUM> arranged behind the first cutter shaft <NUM> seen in the forward direction d1. The second cutter shaft <NUM> is configured to rotate around a second rotational axis ax2. When the cutting deck <NUM> is positioned onto a ground surface <NUM>, the second rotational axis ax2 extends substantially parallel to the ground surface <NUM>. The feature that the second rotational axis ax2 extends substantially parallel to the ground surface <NUM> may encompass that an angle between the second rotational axis ax2 and the ground surface <NUM> is less than <NUM> degrees. The cutting units <NUM> of the second cutter shaft <NUM> are arranged on the second cutter shaft <NUM>. When the second cutter shaft <NUM> is rotating around the second rotational axis ax2, each cutting unit <NUM> of the second cutter shaft <NUM> is rotating in a respective second rotational plane p2. For the reason of brevity, one such second rotational plane p2 is indicated with the reference sign "p2" in <FIG>. The cutting units <NUM> of the second cutter shaft <NUM> are arranged at an axial distance d from each other along the second cutter shaft <NUM>. Since the cutting units <NUM> are arranged on the second rotational axis ax2 and since the second cutter shaft <NUM> is arranged to rotate around the second rotational axis ax2 being substantially parallel to the ground surface <NUM>, each second rotational plane p2 is substantially perpendicular to the ground surface <NUM>. Further, as can be seen in <FIG>, the second rotational plane p2 is angled in relation to the forward direction d1. Due to these features, a cutting deck <NUM> is provided capable of cutting grass in an efficient manner requiring a low amount of energy.

The second rotational plane p2 is angled in relation to the forward direction d1 at a second angle a2. According to the illustrated embodiments, the second angle a2 is approximately <NUM> degrees. According to further embodiments, the second angle a2 may be within the range of <NUM> degrees to <NUM> degrees, or within the range of <NUM> degrees to <NUM> degrees, or within the range of <NUM> degrees to <NUM> degrees.

As can be seen in <FIG>, the second angle a2 is different from the first angle a1. According to the illustrated embodiments, the first and second angles a1, a2 have approximately the same size, namely about <NUM> degrees, but the second angle a2 is measured at an opposite side of a vector d1 indicating the forward direction d1, than the first angle a1. Thus, according to the illustrated embodiments, the first rotational planes p1 are angled counter clockwise in relation to the forward direction d1 seen in a direction towards the ground surface <NUM>, and second rotational planes p2 are angled clockwise in relation to the forward direction d1 seen in a direction towards the ground surface <NUM>. Accordingly, in the illustrated embodiments, the angle between a first rotational plane p1 and a second rotational plane p2 is approximately <NUM> degrees.

According to the illustrated embodiments, each of the first and second cutter shafts <NUM>, <NUM> comprises eight cutting units <NUM>. According to further embodiments, the number of cutting units <NUM> arranged on a cutter shaft <NUM>, <NUM>, <NUM>, <NUM> of the cutting deck <NUM> may be within the range of three to twenty, or within the range of four to twelve.

<FIG> illustrates the lawnmower cutting deck <NUM> illustrated in <FIG>. As indicated in <FIG>, cutting units <NUM> of the second cutter shaft <NUM> are displaced in a direction d2 perpendicular to the forward direction d1 in relation to cutting units <NUM> of the first cutter shaft <NUM> approximately half the distance d' between cutting units <NUM> of the first cutter shaft <NUM> measured in the direction d2 perpendicular to the forward direction d1. That is, points <NUM> in which the second rotational axis ax2 intersects second rotational planes p2 of cutting units <NUM> of the second cutter shaft <NUM> are displaced in the direction d2 approximately half the distance d' relative points <NUM> in which the first rotational axis ax1 intersects first rotational planes p1 of cutting units <NUM> of the first cutter shaft <NUM>. Thereby, the cutting result and the efficiency of cutting is further improved, because cutting units <NUM> of the first and second cutter shafts <NUM>, <NUM> together cover a great area when the cutting deck <NUM> is moved in the forward direction d1, and cutting units <NUM> of the second cutter shaft <NUM> may cut grass that has not been cut by cutting units of the first cutter shaft <NUM>. The distance d' may herein also be defined as the distance d' between rotational planes p1, p2 of cutting units <NUM> measured in the direction d2 perpendicular to the forward direction d1. Correspondingly, the axial distance d, as referred to herein may be defined as the distance d between rotational planes p1, p2 of cutting units <NUM> measured along the rotational axis ax1, ax2 of the cutter shaft <NUM>, <NUM> of the cutting units <NUM>. Further, the distance d' between cutting units <NUM> of the first cutter shaft <NUM> measured in the direction d2 perpendicular to the forward direction d1, may herein also be referred to as a projected distance d' between cutting units <NUM>, or a projected distance d' between rotational planes p1 of cutting units <NUM>, in the forward direction d1. According to the illustrated embodiments, the cutting units <NUM> are arranged at an axial distance d of <NUM> from each other along the respective cutter shaft <NUM>, <NUM>, <NUM>, <NUM>. Because the first rotational planes p1 are angled relation to the forward direction d1 at the first angle a1 being approximately <NUM> degrees, the distance d' between cutting units <NUM> of the first cutter shaft <NUM>, measured in the direction d2 perpendicular to the forward direction d1, is according to the illustrated embodiments approximately <NUM>, and half the distance d' between cutting units <NUM> of the first cutter shaft <NUM>, measured in the direction d2 perpendicular to the forward direction d1, is approximately <NUM>.

According to further embodiments, the axial distance d between cutting units <NUM> along the respective cutter shaft <NUM>, <NUM>, <NUM>, <NUM> may be within the range of <NUM> and <NUM>, or within the range of <NUM> and <NUM>.

In the following, simultaneous reference is made to <FIG> and <FIG>. As mentioned, the cutting deck <NUM> according to the illustrated embodiments comprises a third and a fourth cutter shafts <NUM>, <NUM>. The cutting deck <NUM> comprises a longitudinal centre line <NUM>, which is indicated in <FIG>. The first and second cutter shafts <NUM>, <NUM> are arranged on a first lateral side of the longitudinal centre line <NUM>, and the third and fourth cutter shafts <NUM>, <NUM> are arranged on a second lateral side of the longitudinal centre line <NUM>. The second lateral side is opposite to the first lateral side. According to the illustrated embodiments, the third and fourth cutter shafts <NUM>, <NUM> are mounted as a longitudinal translated mirror image of the first and second cutter shafts <NUM>, <NUM>. The third cutter shaft <NUM> is laterally displaced relative the first cutter shaft <NUM> seen in the forward direction d1. The fourth cutter shaft <NUM> is laterally displaced relative the second cutter shaft <NUM> seen in the forward direction d1.

The first and second cutter shafts <NUM>, <NUM> together forms a first V-formation. The third and fourth cutter shafts <NUM>, <NUM> together forms a second V-formation, which extends into the first V-formation. Furthermore, the second V-formation is displaced a distance in a direction opposite to the forward direction d1 relative the first V-formation. Rotational axes ax1, ax2, ax3, ax4 of the first, the second, the third, and the fourth cutter shafts <NUM>, <NUM>, <NUM>, <NUM> together form a rhomboid. This formation and orientation of cutter shafts <NUM>, <NUM>, <NUM>, <NUM> has proven to provide a good cutting result and a low consumption of energy during operation. However, other formations and orientations of cutter shafts <NUM>, <NUM>, <NUM>, <NUM> are plausible, and the formations and orientations of cutter shafts <NUM>, <NUM>, <NUM>, <NUM> are limited only be the definitions of the appended claims. Purely as examples, the cutting deck <NUM> may comprise only the first cutter shaft <NUM>, the cutting deck <NUM> may comprise only the first and second cutter shafts <NUM>, <NUM>, the cutting deck <NUM> may comprise only the first and third cutter shafts <NUM>, <NUM>, or the cutting deck <NUM> may comprise only the second and fourth cutter shafts <NUM>, <NUM>.

In more detail, the third cutter shaft <NUM> is configured to rotate around a third rotational axis ax3. When the cutting deck <NUM> is positioned onto a ground surface <NUM>, the third rotational axis ax3 extends substantially parallel to the ground surface <NUM>. The feature that the third rotational axis ax3 extends substantially parallel to the ground surface <NUM> may encompass that an angle between the third rotational axis ax3 and the ground surface <NUM> is less than <NUM> degrees. The cutting units <NUM> of the third cutter shaft <NUM> are arranged on the third cutter shaft <NUM>. When the third cutter shaft <NUM> is rotating around the third rotational axis ax3, each cutting unit <NUM> of the third cutter shaft <NUM> is rotating in a respective third rotational plane p3. For the reason of brevity, one such third rotational plane p3 is indicated with the reference sign "p3" in <FIG>. The cutting units <NUM> of the third cutter shaft <NUM> are arranged at an axial distance d from each other along the third cutter shaft <NUM>. Since the cutting units <NUM> are arranged on the third rotational axis ax3 and since the third cutter shaft <NUM> is arranged to rotate around the third rotational axis ax3 being substantially parallel to the ground surface <NUM>, each third rotational plane p3 is substantially perpendicular to the ground surface <NUM>. Further, as can be seen in <FIG>, the third rotational plane p3 is angled in relation to the forward direction d1. Due to these features, a cutting deck <NUM> is provided capable of cutting grass in an efficient manner requiring a low amount of energy.

The third rotational plane p3 is angled in relation to the forward direction d1 at a third angle a3. According to the illustrated embodiments, the third angle a3 is approximately <NUM> degrees. According to further embodiments, the third angle a3 may be within the range of <NUM> degrees to <NUM> degrees, or within the range of <NUM> degrees to <NUM> degrees, or within the range of <NUM> degrees to <NUM> degrees.

As can be seen in <FIG>, the third angle a3 is different from the first angle a1. According to the illustrated embodiments, the first and third angles a1, a3 have approximately the same size, namely about <NUM> degrees, but the third angle a3 is measured at an opposite side of a vector d1 indicating the forward direction d1, than the first angle a1. According to the illustrated embodiments, the first rotational planes p1 are angled counter clockwise in relation to the forward direction d1 seen in the direction towards the ground surface <NUM>, and third rotational planes p3 are angled clockwise in relation to the forward direction d1 seen in a direction towards the ground surface <NUM>. Thus, according to the illustrated embodiments, an angle between a first rotational plane p1 and a third rotational plane p3 is approximately <NUM> degrees. Further, as can be seen in <FIG>, the third rotational plane p3 is substantially parallel to the second rotational plane p2.

According to the illustrated embodiments, each of the first and third cutter shafts <NUM>, <NUM> comprises eight cutting units <NUM>. According to further embodiments, the number of cutting units <NUM> arranged on a cutter shaft <NUM>, <NUM>, <NUM>, <NUM> of the cutting deck <NUM> may be within the range of three to twenty, or within the range of four to twelve.

According to the illustrated embodiments, and as indicated in <FIG>, a distance d' between a point <NUM> in which the third rotational axis ax3 intersects a third rotational plane p3 of a cutting unit <NUM>' of the third cutter shaft <NUM> and a point <NUM> in which the first rotational axis ax1 intersects a first rotational plane p1 of a cutting unit <NUM>' of the first cutter shaft <NUM>, measured in a direction d2 perpendicular to the forward direction d1, substantially corresponds to a distance d' between first rotational planes p1 of cutting units <NUM> of the first cutter shaft <NUM> measured in the direction d2 perpendicular to the forward direction d1. Further, according to the illustrated embodiments, the distance d' between a point <NUM> in which the third rotational axis ax3 intersects a third rotational plane p3 of a cutting unit <NUM>' of the third cutter shaft <NUM> and a point <NUM> in which the first rotational axis ax1 intersects a first rotational plane p1 of a cutting unit <NUM>' of the first cutter shaft <NUM>, measured in a direction d2 perpendicular to the forward direction d1, substantially corresponds to a distance d' between third rotational planes p3 of cutting units <NUM> of the third cutter shaft <NUM> measured in the direction d2 perpendicular to the forward direction d1. Thus, according to the illustrated embodiments, cutting units <NUM> of the first cutter shaft <NUM> and cutting units <NUM> of the third cutter shaft <NUM> are arranged at positions of the respective cutter shaft <NUM>, <NUM> resulting in substantially equal distances d' between points <NUM> in which rotational planes p1, p3 of the cutting units <NUM> intersect the respective rotational axis ax1, ax3 along the direction d2 perpendicular to the forward direction d1. As a result thereof, the cutting result is further improved, because during movement of the cutting deck <NUM> in the forward direction d1, the cutting units <NUM> may cut a respective portion of a lawn, wherein the portions are substantially equally spaced along the direction d2 perpendicular to the forward direction d1.

According to the illustrated embodiments, the fourth cutter shaft <NUM> is arranged behind the third cutter shaft <NUM> seen in the forward direction d1. The fourth cutter shaft <NUM> is configured to rotate around a fourth rotational axis ax4. When the cutting deck <NUM> is positioned onto a ground surface <NUM>, the fourth rotational axis ax4 extends substantially parallel to the ground surface <NUM>. The feature that the fourth rotational axis ax4 extends substantially parallel to the ground surface <NUM> may encompass that an angle between the fourth rotational axis ax4 and the ground surface <NUM> is less than <NUM> degrees. The cutting units <NUM> of the fourth cutter shaft <NUM> are arranged on the fourth cutter shaft <NUM>. When the fourth cutter shaft <NUM> is rotating around the fourth rotational axis ax4, each cutting unit <NUM> of the fourth cutter shaft <NUM> is rotating in a respective fourth rotational plane p4. For the reason of brevity, one such fourth rotational plane p4 is indicated with the reference sign "p4" in <FIG>. The cutting units <NUM> of the fourth cutter shaft <NUM> are arranged at an axial distance d from each other along the fourth cutter shaft <NUM>. Since the cutting units <NUM> are arranged on the fourth rotational axis ax4 and since the fourth cutter shaft <NUM> is arranged to rotate around the fourth rotational axis ax4 being substantially parallel to the ground surface <NUM>, each fourth rotational plane p4 is substantially perpendicular to the ground surface <NUM>. Further, as can be seen in <FIG>, the fourth rotational plane p4 is angled in relation to the forward direction d1. Due to these features, a cutting deck <NUM> is provided capable of cutting grass in an efficient manner requiring a low amount of energy.

The fourth rotational plane p4 is angled in relation to the forward direction d1 at a fourth angle a4. According to the illustrated embodiments, the fourth angle a4 is approximately <NUM> degrees. According to further embodiments, the fourth angle a4 may be within the range of <NUM> degrees to <NUM> degrees, or within the range of <NUM> degrees to <NUM> degrees, or within the range of <NUM> degrees to <NUM> degrees.

As can be seen in <FIG>, the fourth angle a4 is different from the third angle a3. According to the illustrated embodiments, the third and fourth angles a3, a4 have approximately the same size, namely about <NUM> degrees, but the fourth angle a4 is measured at an opposite side of a vector d1 indicating the forward direction d1, than the third angle a3. According to the illustrated embodiments, the fourth rotational planes p4 are angled counter clockwise in relation to the forward direction d1 seen in the direction towards the ground surface <NUM>, and the third rotational planes p3 are angled clockwise in relation to the forward direction d1 seen in a direction towards the ground surface <NUM>. Thus, according to the illustrated embodiments, an angle between a third rotational plane p3 and a fourth rotational plane p4 is approximately <NUM> degrees. Further, as can be seen in <FIG>, the fourth rotational plane p4 is substantially parallel to the first rotational plane p1.

Further, as is indicated in <FIG>, cutting units <NUM> of the fourth cutter shaft <NUM> are displaced in a direction d2 perpendicular to the forward direction d1 in relation to cutting units <NUM> of the third cutter shaft <NUM> approximately half the distance d' between cutting units <NUM> of the third cutter shaft <NUM> measured in the direction d2 perpendicular to the forward direction d1. That is, points <NUM> in which the fourth rotational axis ax4 intersects fourth rotational planes p4 of cutting units <NUM> of the fourth cutter shaft <NUM> are displaced in the direction d2 approximately half the distance d' relative points <NUM> in which the third rotational axis ax3 intersects third rotational planes p3 of cutting units <NUM> of the third cutter shaft <NUM>. Thereby, the cutting result and the efficiency of cutting is further improved, because cutting units <NUM> of the third and fourth cutter shafts <NUM>, <NUM> together cover a great area when the cutting deck <NUM> is moved in the forward direction d1, and cutting units <NUM> of the fourth cutter shaft <NUM> may cut grass that has not been cut by cutting units of the third cutter shaft <NUM>. The distance d' may also be defined as the distance d' between rotational planes p3, p4 of cutting units <NUM> measured in the direction d2 perpendicular to the forward direction d1. Correspondingly, the axial distance d, as referred to herein may be defined as the distance d between rotational planes p3, p4 of cutting units <NUM> measured along the rotational axis ax3, ax4 of the cutter shaft <NUM>, <NUM> of the cutting units <NUM>. According to the illustrated embodiments, the cutting units <NUM> are arranged at an axial distance d of <NUM> from each other along the respective cutter shaft <NUM>, <NUM>, <NUM>, <NUM>. Because the third rotational planes p3 are angled relation to the forward direction d1 at the third angle a3 being approximately <NUM> degrees, the distance d' between cutting units <NUM> of the third cutter shaft <NUM>, measured in the direction d2 perpendicular to the forward direction d1, is approximately <NUM>, and half the distance d' between cutting units <NUM> of the third cutter shaft <NUM>, measured in the direction d2 perpendicular to the forward direction d1, is approximately <NUM>.

According to the illustrated embodiments, and as indicated in <FIG>, a distance d' between a point <NUM> in which the fourth rotational axis ax4 intersects a fourth rotational plane p4 of a cutting unit <NUM>' of the fourth cutter shaft <NUM> and a point <NUM> in which the second rotational axis ax2 intersects a second rotational plane p2 of a cutting unit <NUM>' of the second cutter shaft <NUM> measured in a direction d2 perpendicular to the forward direction d1, substantially corresponds to a distance d' between second rotational planes p2 of cutting units <NUM> of the second cutter shaft <NUM> measured in the direction d2 perpendicular to the forward direction d1. Further, according to the illustrated embodiments, the distance d' between a point <NUM> in which the fourth rotational axis ax4 intersects a fourth rotational plane p4 of a cutting unit <NUM>' of the fourth cutter shaft <NUM> and a point <NUM> in which the second rotational axis ax2 intersects a second rotational plane p2 of a cutting unit <NUM>' of the second cutter shaft <NUM>, measured in a direction d2 perpendicular to the forward direction d1, substantially corresponds to a distance d' between fourth rotational planes p4 of cutting units <NUM> of the fourth cutter shaft <NUM> measured in the direction d2 perpendicular to the forward direction d1. Thus, according to the illustrated embodiments, cutting units <NUM> of the second cutter shaft <NUM> and cutting units <NUM> of the fourth cutter shaft <NUM> are arranged at positions of the respective cutter shaft <NUM>, <NUM> resulting in substantially equal distances d' between points <NUM> in which rotational planes p1, p4 of the cutting units <NUM> intersect the respective rotational axis ax2, ax4 along the direction d2 perpendicular to the forward direction d1. As a result thereof, the cutting result is further improved, because during movement of the cutting deck <NUM> in the forward direction d1, the cutting units <NUM> of the second and fourth cutter shafts <NUM>, <NUM> may cut a respective portion of a lawn, wherein the portions are substantially equally spaced along the direction d2 perpendicular to the forward direction d1.

According to the illustrated embodiments, and as is indicated in <FIG>, the cutting deck <NUM> comprises a first electric motor e1 configured to rotate the first cutter shaft <NUM>, a second electric motor e2 configured to rotate the second cutter shaft <NUM>, a third electric motor e3 configured to rotate the third cutter shaft <NUM>, and a fourth electric motor e4 configured to rotate the fourth cutter shaft <NUM>. The electric motors e1, e2, e3, e4 may be configured to rotate the cutter shafts <NUM>, <NUM>, <NUM>, <NUM> directly, or via a transmission. According to further embodiments, the cutting deck <NUM>, or a lawnmower comprising the cutting deck <NUM>, may comprise one electric motor configured to rotate one or more cutter shafts <NUM>, <NUM>, <NUM>, <NUM> of the cutting deck <NUM>. The electric motors e1, e2, e3, e4 may be configured to rotate the cutter shafts <NUM>, <NUM>, <NUM>, <NUM> in rotational directions causing portions the cutting units <NUM> below their respective rotational axis ax1, ax2, ax3, ax4 to move in tangential directions having components in the forward direction d1. Further, the electric motors e1, e2, e3, e4 may be configured to rotate the cutter shafts <NUM>, <NUM>, <NUM>, <NUM> in rotational speeds ensuring that a kinetic energy of each cutting member <NUM> is below a predetermined threshold value and/or is within a predetermined range, wherein such a predetermined threshold value and/or an endpoint of such a predetermined range may be a value according to any of the examples given herein, such as <NUM> Joules, or <NUM> Joules. Further, the electric motors e1, e2, e3, e4 may be configured to rotate the cutter shafts <NUM>, <NUM>, <NUM>, <NUM> in rotational speeds ensuring that a maximum attainable velocity of a point which is half way along the reckonable length of each cutting member <NUM> is below a predetermined threshold value, and/or ensuring that a rotational speed of each cutter shaft <NUM>, <NUM>, <NUM>, <NUM> is below a predetermined threshold value.

As is evident from <FIG> and <FIG>, and from the above, according to the illustrated embodiments, cutting units <NUM> of a cutter shaft <NUM>, <NUM>, <NUM>, <NUM> are configured to cut in axially spaced, mutually parallel, planes p1, p2, p3, p4.

<FIG> illustrates a front view of the cutting deck <NUM>, illustrated in <FIG>, <FIG> and <FIG>. In <FIG>, the cutting deck <NUM> is illustrated as being viewed in a direction opposite to the forward direction. According to the illustrated embodiments, the cutting deck <NUM> comprises wheels <NUM> configured to support the cutting deck <NUM> at an adjustable height over a ground surface <NUM>. According to the illustrated embodiments, the cutting deck <NUM> comprises a guiding member <NUM> arranged between each adjacent pair of cutting units <NUM>. Thereby, a further efficient cutting is provided, because the guiding members <NUM> will guide grass towards rotational planes of the cutting members <NUM>. In addition, the guiding members <NUM> may ensure that a distance is obtained between rotors of the cutting units <NUM> and a ground surface <NUM>, also when the cutting deck <NUM> is moved over an uneven ground surface <NUM>. Still further, one or more of the guiding members <NUM> may bump into an object on the ground surface <NUM>, such as a stone or stump, instead of one or more cutting units <NUM>. As a result thereof, the operational reliability of the cutting deck <NUM> is further improved. For the reason of brevity and clarity, In <FIG>, only some of the cutting units <NUM> are indicated with the reference sign "<NUM>" and only some of the guiding members <NUM> are indicated with the reference sign "<NUM>".

Further, as is evident from <FIG>, the cutting units <NUM> of the cutting deck <NUM> are substantially equally spaced in the direction d2 opposite to the forward direction. As a result thereof, the cutting result is further improved, because during movement of the cutting deck <NUM> in the forward direction, the cutting units <NUM> may cut a respective portion of a lawn, wherein the portions are substantially equally spaced along the direction d2 perpendicular to the forward direction.

<FIG> illustrates a lawnmower <NUM> according to some embodiments. The lawnmower <NUM> comprises a lawnmower cutting deck <NUM> according to the embodiments illustrated in <FIG>, <FIG>, <FIG>, and <FIG>. In <FIG>, one wheel <NUM> of the wheels <NUM> of the cutting deck <NUM> is visible. The wheels <NUM> constitutes front wheels of the lawnmower <NUM> according to the illustrated embodiments. The lawnmower <NUM> further comprises rear wheels <NUM> each powered by an electric motor. The cutting deck <NUM> of the lawnmower <NUM> comprises a housing <NUM> covering upper portions of all cutting units of the cutting deck <NUM>.

According to the embodiments illustrated in <FIG>, the lawnmower <NUM> is a self-propelled robotic lawnmower <NUM> capable of mowing a lawn in an autonomous manner without the intervention of a user. The lawnmower <NUM> may comprise one or more batteries arranged to supply electricity to electric motors of the lawnmower <NUM>. According to the illustrated embodiments, the lawnmower <NUM> comprises a control unit <NUM>. The lawnmower <NUM> may further comprise one or more sensors connected to the control unit <NUM>, wherein the one or more sensors may be arranged to sense a magnetic field of a wire, and/or an impending or ongoing collision event with an object. The lawnmower <NUM> may comprise one or more positioning units configured to estimate a current position of the lawnmower <NUM>. According to the illustrated embodiments, the lawnmower <NUM> comprises a communication unit <NUM> connected to the control unit <NUM>. The communication unit <NUM> is configured to communicate with a remote communication unit <NUM>' 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 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 <NUM> to <NUM>.

The control unit <NUM> may be configured to navigate the lawnmower <NUM> in a systematic and/or random pattern to mow an area. The control unit <NUM> may navigate the lawnmower <NUM> using input from the one or more sensors, the one or more positioning units, and/or communication unit <NUM>. The control unit <NUM> may navigate the lawnmower <NUM> by controlling rotational speed of wheels <NUM> of the lawnmower <NUM>. The lawnmower <NUM> may be configured to mow lawns, gardens, parks, sports fields, golf courts and the like. The control unit <NUM> may be configured to navigate the lawnmower <NUM> in a manner such that the cutting deck <NUM> mainly is moved in the forward direction d1, indicated in <FIG>.

According to the embodiments illustrated in <FIG>, the self-propelled robotic lawnmower <NUM> may be arranged such that a kinetic energy of each cutting member of the cutting deck <NUM>, during operation of the robotic lawnmower <NUM>, is below <NUM> Joules, for example such that a kinetic energy of each cutting member of the cutting deck <NUM> is within the range of <NUM> Joules and <NUM> Joules.

<FIG> illustrates a lawnmower <NUM>' according to some further embodiments. The lawnmower <NUM>' comprises a lawnmower cutting deck <NUM> according to the embodiments illustrated in <FIG>, <FIG>, <FIG>, and <FIG>. According to the illustrated embodiments, the lawnmower <NUM>' is a riding mower <NUM>' comprising a seat <NUM> for an operator. Further the lawnmower <NUM>' comprises a steering device <NUM>, such as a steering wheel, and a motor <NUM> configured to provide motive power to the lawnmower <NUM>'. The motor <NUM> may comprise a combustion engine and/or an electric motor. Also in these embodiments, the cutting deck <NUM> of the lawnmower <NUM>' comprises a housing <NUM> covering upper portions of all cutting units of the cutting deck <NUM>. The lawnmower <NUM>' may be configured to mow lawns, gardens, parks, sports fields, golf courts and the like. The forward direction d1 of the cutting deck <NUM> is indicated with the arrow "d1".

According to the embodiments illustrated in <FIG>, the riding mower <NUM>' may be arranged such that a kinetic energy of each cutting member of the cutting deck <NUM>, during operation of the riding mower <NUM>', is below <NUM> Joules, for example such that a kinetic energy of each cutting member of the cutting deck <NUM> is within the range of <NUM> Joules and <NUM> Joules, or is within the range of <NUM> Joules and <NUM> Joules, or is within the range of <NUM> Joules and <NUM> Joules.

<FIG> illustrates a method <NUM> of mowing a lawn. Steps of the method <NUM> may be performed using a cutting deck <NUM> according to the embodiments illustrated in <FIG>, <FIG>, <FIG>, and <FIG>. Therefore, below, simultaneous reference is made to <FIG>, <FIG>, <FIG>, <FIG>, and <FIG>.

Claim 1:
A lawnmower cutting deck (<NUM>), wherein the cutting deck (<NUM>) is configured to be moved in a forward direction (d1) over a ground surface (<NUM>) to cut grass, the cutting deck (<NUM>) comprising:
- at least a first cutter shaft (<NUM>), and
- at least one cutting unit (<NUM>) arranged on the first cutter shaft (<NUM>),
wherein the first cutter shaft (<NUM>) is configured to rotate around a first rotational axis (ax1) extending substantially parallel to the ground surface (<NUM>) to rotate the at least one cutting unit (<NUM>) in a first rotational plane (p1), and wherein the first rotational plane (p1) is angled in relation to the forward direction (d1) at a first angle (a1) within the range of <NUM> degrees to <NUM> degrees, or within the range of <NUM> degrees to <NUM> degrees, wherein the cutting deck (<NUM>) comprises a second cutter shaft (<NUM>) and at least one cutting unit (<NUM>) arranged on the second cutter shaft (<NUM>), wherein the second cutter shaft (<NUM>) is configured to rotate around a second rotational axis (ax2) extending substantially parallel to the ground surface (<NUM>) to rotate the at least one cutting unit (<NUM>) in a second rotational plane (p2), wherein the second rotational plane (p2) is angled in relation to the forward direction (d1) at a second angle (a2) within the range of <NUM> degrees to <NUM> degrees, or within the range of <NUM> degrees to <NUM> degrees, and wherein the second angle (a2) is different from the first angle (a1), characterized in that the second cutter shaft (<NUM>) is arranged behind the first cutter shaft (<NUM>) seen in the forward direction (d1).