Patent Description:
A hedge trimmer is a type of outdoor gardening tool that is used to cut branches and leaves, for example to shape a hedge to a desired, typically geometric, shape. Various solutions for hedge trimming are known and accessible on the market, both manual and automatic or semi-automatic.

In fact, manual solutions are available, where the cutting work is usually done by a person holding the hedge trimmer, typically with both hands, and moving the cutting blade along the shape of the hedge. The cutting blade is typically elongated in shape and consists of a support rod and two blades, each with a plurality of teeth, driven by a motor to make an alternating cutting motion. Manual hedge trimmers are usually used for trimming and adjusting hedges or bushes, preferably small ones, as it is time-consuming and unsafe in terms of safety, and at the same time it is also difficult to achieve uniform cutting quality requirements.

Alternatively, automatic or semi-automatic solutions are available, in which the cutting blade is mounted on a vehicle, typically a small tractor or carriage, where the user drives the vehicle (motorised or non-motorised). The cutting blade is typically oriented in a vertical and/or horizontal direction with respect to the ground, for lateral and/or upper pruning of plants, respectively, and the cutting blade is fixed or substantially fixed during use with respect to this orientation. These apparatuses are complicated and costly to produce and operate, maintenance-intensive and relatively complicated to use.

In addition, in the version used for domestic (non-agricultural) pruning, these apparatuses make a cut that is constrained to the direction of the cutting blade. The cutting blade is typically constrained to the vehicle. The direction of the cutting blade, and therefore of the cutting line, is strongly influenced by the shape of the ground on which the vehicle is moving.

Therefore, on uneven or sloping ground, the use of this apparatus may not be suitable for a correct and regular cut of the hedge.

For example, patent document ITTV20120172A1 discloses a mobile hedge cutting machine in which the vertical cutting member is kept in a constant position with respect to a predetermined positional reference, but without taking into account the direction and/or speed of the carriage, and therefore without any possibility of precise cutting of the hedge and without any particular freedom to customise the cut.

Furthermore, patent document <CIT> discloses a device forming a hedge trimmer that can be easily mounted on a commercial motorised machine, such as a micro-tractor or lawn tractor, in which the direction of the cutting blade is adjusted by reference cables positioned along the path, and in which a portion of the hedge trimmer is in contact with the cable during the hedge trimming operation.

The general aim of the present invention is to overcome the above-mentioned drawbacks related to the known state of the art.

This general object and other more specific objects are reached thanks to what is expressed in the appended claims that form an integral part of the present description.

The present invention shall become more readily apparent from the detailed description that follows to be considered together with the accompanying drawings in which:.

For the illustration of the drawings, use is made in the following description of identical or similar numerals to indicate construction elements with the same function. Further, for illustration clarity, some numerical references may not be repeated in all the figures.

Indications such as "vertical" and "horizontal", "upper" and "lower" (in the absence of other indications) are to be read with reference to the assembly (or operating) conditions and with reference to the normal terminology used in everyday language, where "vertical" indicates a substantially parallel direction to that of the gravitational force vector "g" and horizontal to a direction perpendicular thereto, coinciding with the "direction of the horizon".

With general reference to the various figures, a preferred, but not limiting, embodiment of a mobile hedge trimmer apparatus according to the present invention is shown, indicated in its entirety by the numerical reference <NUM>.

It will be referred to below with the abbreviated notation "apparatus <NUM>". It has to be noted that in <FIG> and in <FIG> further embodiments of the mobile hedge trimmer apparatus according to the present invention are shown (these will hereinafter be referred to by the notation "apparatus <NUM>" and "apparatus <NUM>"), which differ from apparatus <NUM> in particular due to the movement means and the way in which the apparatus moves along a path over a ground (whereby ground is to be understood as the portion on which the apparatus rests, which may be for example the lawn of a garden or the enclosing wall of a property).

The apparatus <NUM> constitutes an integrated system which, as will be seen, is capable of automatically adapting its cutting line according to the conformation of the ground on which the apparatus is used. In particular, the apparatus <NUM> is able to compensate for any inclination or unevenness of the ground in order to maintain the desired height of the cutting blade, being able to obtain various hedge cutting directions, for example parallel to the horizontal direction or inclined with respect to the horizontal direction (see <FIG>).

According to a preferred embodiment, the apparatus <NUM> substantially comprises two portions <NUM> and <NUM> and, as a whole, appears as shown exemplified in <FIG> and <FIG>.

In particular, the first portion <NUM> acts as a mobile base of the apparatus <NUM> adapted to rest on a ground and advancing along a path, and the second portion <NUM>, mechanically connected to the first portion <NUM>, is dedicated to cutting and protrudes from the base of the apparatus <NUM>. It has to be noted that the path on which the apparatus <NUM> advances may be a predefined path, for example marked by detectors or sensors or guides placed in the vicinity of the hedge being cut, or it may be defined by the user by moving the apparatus <NUM>, as further explained below. It is further to be noted that the apparatus <NUM> may rest on a portion of the ground that varies along the path taken due to the advancement thereof; when the apparatus <NUM> rests on a portion of the ground, the apparatus <NUM>, in particular the first portion <NUM>, defines a plane that may be inclined with respect to a horizontal plane, for example in the case where the portion of the ground on which it rests has unevenness and/or depressions.

With reference to the embodiment shown in <FIG>, the first portion <NUM> essentially comprises two pairs of wheels, 104a and 104b, for moving the apparatus <NUM> and a plate <NUM>, for example a substantially square shaped plate which, as will become clear later, serves as a support for the second portion <NUM> and further elements of the apparatus <NUM>. It has to be noted that according to alternative embodiments, shown for example in <FIG>, the first portion <NUM> may comprise a different number of wheels, but generally comprises at least two wheels. It has to be noted that an embodiment comprising three wheels (not shown in the figures) is also easily implemented according to the teachings of the present invention.

According to a preferred embodiment, the apparatus <NUM> is motorised, i.e. the wheels are moved by a motor <NUM>.

Alternatively, the apparatus <NUM> may be moved by means of mechanical tracks, also moved by a motor <NUM>.

With reference to <FIG>, the front wheels 104a and the rear wheels 104b are hinged to a support <NUM>. This support <NUM> is in turn pivoted to the ends of two uprights <NUM>. Advantageously, the two uprights <NUM> are positioned on the lower part of the plate <NUM> so as to form an "X" in which the ends of the uprights <NUM> are placed at the four corners of the plate <NUM>.

Advantageously, the wheels 104a and 104b work in pairs: both the front wheels 104a and the rear wheels 104b are steerable wheels and the wheels 104a are also traction wheels.

With reference to <FIG>, the wheels 104a and 104b are designed to steer by means of a linkage capable of turning the wheels about the end of the upright <NUM>.

In particular, the supports <NUM> of the wheels 104a and the supports <NUM> of the wheels 104b are pivoted to a first end of a first lever <NUM>. Said lever <NUM> is pivoted at one end to a second lever <NUM>.

The lever <NUM> transmitting the steering movement to a first wheel 104a and the lever <NUM> transmitting the steering movement to a second wheel 104a are rigidly connected to each other by means of a toothed bar <NUM>.

Similarly, the lever <NUM> of a first wheel 104b and the lever <NUM> of a second wheel 104b are also rigidly connected to each other by means of a toothed bar <NUM>; in particular, one end of the lever <NUM> of a first wheel 104b and one end of the lever <NUM> of a second wheel 104b are connected to the toothed bar <NUM> so that the toothed bar <NUM> can rigidly translate by transmitting movement to the respective levers <NUM> of the wheels 104a, 104b.

The toothed bar <NUM> is designed to run on the toothing of a pinion <NUM> located in the lower part of the plate <NUM>, i.e. the part of the plate facing the ground.

The pinion <NUM> is rotated by a motor, in particular a servomotor, controlled by a user as explained later.

When the servomotor activates the rotation of the pinion <NUM>, the toothed bar <NUM> and the respective levers <NUM> rigidly translate in a horizontal direction in a first sense or in a second sense, causing the respective wheels to be steered in a first sense or in a second sense.

Alternatively, the wheels 104a and the wheels 104b may be mutually independent steerable wheels, wherein each wheel 104a and 104b is mechanically connected to a servomotor that specifically controls the steering thereof.

Advantageously and referring to <FIG>, the first portion <NUM> further comprises a handlebar <NUM> adapted to be operated by a user.

In particular, the handlebar <NUM> comprises a substantially horizontal guide bar pivoted to the first portion <NUM>, in particular to the plate <NUM>, by at least one, advantageously two, support rods.

Advantageously, one or more joysticks including a lever adapted to be operated by a user to define the traction direction and/or the traction speed can be installed on the guide bar.

Alternatively, one or more load cells <NUM> may be installed on the guide bar adapted to detect at least one force exerted on the handlebar <NUM>, in particular at least one pressure exerted by a user on the guide bar, so that, based on the direction of the force exerted, for example forward or backward, i.e. a force having the sense of the horizontal component directed towards the front wheels 104a or towards the rear wheels 104b, the traction direction, in particular the traction sense, of the apparatus <NUM> is defined.

Further, based on the intensity of the force (pressure) detected by the load cells <NUM>, the traction speed of the apparatus <NUM> is defined: a higher pressure corresponds to a higher speed and a lower pressure corresponds to a lower speed; obviously, a zero pressure corresponds to a zero speed.

According to an example embodiment, the advancement of the apparatus <NUM> can be defined by a user by moving a joystick, for example a three-axis joystick placed on the handlebar <NUM>.

Advantageously, by using two joysticks, e.g. two dual-axis joysticks on the handlebars <NUM>, the displacement direction of the apparatus <NUM> can be further defined.

Typically, the apparatus <NUM> may move along a direction parallel to the extension direction of the hedge being cut; in other words, the apparatus <NUM> may be side by side with the hedge and move along a path parallel to the extension direction of the hedge. It has to be noted that the extension direction of the hedge can be linear or it can have any non-linear direction, e.g. curved or with direction change angles along the extension of the hedge.

In some cases, it may be advantageous to change the displacement direction of the apparatus <NUM> in relation to the extension direction of the hedge, e.g. to avoid obstacles or to move closer to/further away from the hedge to vary the vertical cutting line.

According to an embodiment shown in <FIG> and <FIG>, the handlebar can be translated in a first direction, perpendicular to the extension direction of the hedge and in particular directed towards the hedge, or in a second direction, opposite to the first one, that is directed in the opposite sense to the extension direction of the hedge; basically, translating the handlebar in the first direction causes a movement towards the hedge, and translating the guide bar in the second direction causes a movement away from the hedge.

Alternatively, the displacement direction of the apparatus <NUM> may be defined by at least one, preferably two joysticks or load cells <NUM> placed on the handlebar guide bar <NUM>, in particular by movement of the joystick lever by the user or by different pressure exerted by the user on the load cells <NUM>.

The handlebars <NUM> and its components are advantageously connected to a control unit <NUM> which receives electrical or electronic signals as input from them and sends command signals to the servo motor which rotates the pinions <NUM> of the steering system and to the traction motor connected to the traction wheels of the apparatus <NUM>.

Advantageously and as will be described below, the first portion <NUM> further comprises sensors and measuring and/or control devices.

As already mentioned, the second portion <NUM> is mechanically connected to the first portion <NUM>.

With reference to <FIG> and <FIG>, the second portion <NUM> comprises a pillar <NUM> pivoted to the first portion <NUM> and capable of tilting on two axes A and B perpendicular to each other. Preferably, as shown in the figures, the axis A is parallel to the extension direction of the hedge and the axis B is perpendicular to the extension direction of the hedge.

In particular, the pillar <NUM> can be inclined or tilted (with respect to a zero reference position, typically coinciding with the vertical direction) using a movement system for each axis A and B.

According to a preferred embodiment shown in <FIG>, the movement system of the pillar <NUM> comprises a servomotor <NUM>, a worm screw <NUM>, a rod <NUM> and a slider having a threaded cavity.

In this particular embodiment, the pillar <NUM> has a square cross-section.

In particular, the rod <NUM> consists of two levers that are parallel to each other.

A first end of the levers of the rod <NUM> is constrained to the pillar <NUM>, in particular a first lever is connected to a first side of the pillar <NUM> and a second lever is connected to a second side of the pillar <NUM> opposite the first one, so that the levers are parallel and spaced apart from each other by the thickness of the pillar <NUM>.

The slider is connected to the second end of the levers of the <NUM>.

In particular, the slider is positioned between the two levers, e.g. it is pivoted between the two levers.

The slider has a threaded cavity into which the worm screw <NUM> is inserted.

In particular, the worm screw <NUM> is adapted to rotate in a clockwise or anticlockwise direction, being moved by the servomotor <NUM>.

The worm screw <NUM> is adapted to transmit, by means of its rotation, a translational motion to the slider and consequently to the rod <NUM>.

In this way, a translation movement of the rod <NUM> corresponds to an inclination of the pillar <NUM>.

Alternatively, the threaded slider may act as a nut screw and rotate with respect to the worm screw <NUM> being placed by the servomotor <NUM> via a mechanical connection between the slider and the servomotor, for example by means of toothed pinions connected to the levers of the rod <NUM>; during the rotational motion of the slider about the worm screw <NUM>, the slider transmits a translational motion to the worm screw <NUM>.

Alternatively, the movement of the pillar <NUM> can be implemented with other different movement systems; for example, the rod <NUM> can be connected and moved by hydraulic pistons, or gear motors can be used, directly connected to the pillar 250pillar.

Advantageously, a first movement system is adapted to tilt the pillar in direction A and a second movement system is adapted to tilt the pillar in direction or B.

In particular, the servomotors <NUM> (more generally, the pillarmovement system of the pillar <NUM>) are controlled by a control unit <NUM> (see <FIG>) operating by means of dedicated software which, as will be further explained below, is adapted to receive information from sensors of the apparatus <NUM> and consequently adjust the position of one or more cutting blades of the apparatus <NUM>.

With reference to <FIG> and <FIG>, at least one cutting blade is constrained to the pillar <NUM>, in particular a first cutting blade <NUM>, perpendicular to the direction of the axis of the pillar <NUM>, and a second cutting blade <NUM> parallel to the direction of the axis of the pillar <NUM>.

It has to be noted that a typical hedge trimmer blade is made up of blades with double serrated teeth sliding relative to each other.

Advantageously, the first cutting blade <NUM> can comprise two or more modules that can slide telescopically relative to each other.

According to a preferred example embodiment, the relative movement between the blades of the first cutting blade <NUM> and the second cutting blade <NUM> is operated by a belt drive system integral with at least two connecting rods connected to the first cutting blade <NUM> and the second cutting blade <NUM>, respectively; alternatively, hydraulic pistons or electric motors may be used.

The first cutting blade <NUM> is adapted to cut an upper profile of the hedge, while the second cutting blade <NUM> is adapted to cut a side profile of the hedge.

In particular, the first cutting blade <NUM> is installed on a runner <NUM>, the runner <NUM> being adapted to slide along a sliding guide, for example a rail, constrained to the pillar <NUM>.

Advantageously, the first cutting blade <NUM> is installed on the runner <NUM> by means of a quick coupling, for example by means of a bayonet coupling, so that it can be easily replaced and/or interchanged with different types of cutting blades. According to a preferred embodiment, the sliding of the runner <NUM> is driven by a dedicated servomotor, which is also controlled by the control unit <NUM>, so that the position of the runner <NUM> along the pillar <NUM> can vary, in particular according to the inclination of the ground with respect to a horizontal plane (and therefore of the first portion <NUM>) and/or bumps and/or depressions on the ground.

In particular, the control unit <NUM> receives as input parameters and/or measurements and outputs an activating or deactivating command of the servomotor of the runner <NUM>.

As already mentioned, the control unit <NUM> receives as input the parameters set by the user via the human-machine interface <NUM>.

The control unit <NUM> may further receive measurements from inclinometers and/or gyroscopes or any other inclination detecting tool and/or accelerometers and/or barometers and/or motion sensors and/or advancement detectors (e.g. encoders) present on, for example, the first portion <NUM> or the second portion <NUM>. In particular, motion sensors or advancement detectors may detect a direction and/or speed of travel of the apparatus <NUM>.

The control unit <NUM> is adapted to receive information from the sensors repeatedly, in particular periodically: for example, the sensors present on the apparatus <NUM> can collect data every <NUM> (milliseconds), i.e. substantially in real time, and the control unit <NUM> can adjust the inclination of the pillar <NUM> and/or the position of the first cutting blade <NUM> along the pillar with a time response comparable to that of data collection, i.e. substantially in real time. Advantageously, the data collection frequency and/or the control frequency can be set by the user. According to an example embodiment, the user may have the option of defining a tolerance of the inclination of the pillar <NUM> with respect to the vertical direction, for example a tolerance of <NUM>° with respect to the vertical direction. Even more advantageously, the user may have the possibility of defining a range of inclination with respect to the vertical direction in which the servomotor(s) controlling the movement system of the pillar <NUM> reduce their speed, so as to define a "slowing down zone" of the movement of the pillar <NUM> in proximity to the vertical direction. In particular, the wider the set range, e.g. <NUM>° - <NUM>°, the "softer" the inclination adjustment movement, and the narrower the set range, e.g. <NUM>° - <NUM>°, the "nervous" the inclination adjustment movement. Advantageously, the operation of the control unit <NUM> can also be linked to the advancement speed of the apparatus <NUM>. For example, depending on the frequency of data collection and/or the tolerances set by the user, the control unit <NUM> can adjust the advancement speed of the apparatus <NUM>. In particular, in the event that the adjustment of the inclination of the pillar <NUM> and/or the position of the first cutting blade <NUM> along the pillar <NUM> cannot be correctly carried out, the control unit <NUM> may decrease - possibly even cancel - the advancement speed of the apparatus until the desired adjustment has been made.

Advantageously, the control unit <NUM> is further connected to a human-machine interface <NUM>, in particular a display and/or buttons and/or a joystick.

The human-machine interface <NUM> is located, for example, on the handlebar <NUM> of the apparatus <NUM> (see <FIG> and <FIG>), so that the user can easily set cutting adjustment parameters of the apparatus <NUM>, for example the shape of the cut of the desired upper portion of the hedge, which, as explained below, can be, for example, parallel to the horizon line or inclined with respect to the horizon line or with parallel sections and perpendicular sections to the horizon line ("stepped" cutting). According to a preferred embodiment, there are two inclinometers: a first inclinometer placed on the plate <NUM> and a second inclinometer placed on the pillar <NUM>. Advantageously, there may be a third inclinometer placed on the first cutting blade <NUM>.

According to this preferred embodiment, the inclinometers send to the control unit <NUM> data on the inclination of the plate <NUM> (and consequently of the ground) with respect to a horizontal plane and/or on the inclination of the first cutting blade <NUM> and/or on the inclination of the second cutting blade <NUM>, in a first direction A and in a second direction B.

It has to be noted that an inclination of the second cutting blade <NUM> is equivalent to an inclination of the pillar <NUM> of the same magnitude, the second cutting blade <NUM> being constrained to the pillar <NUM>, in particular in a direction parallel to the axis of the pillar <NUM>.

The control unit <NUM>, when it receives as input values of inclination of the second cutting blade <NUM> other than zero in direction A and/or in direction B, i.e., when the pillar <NUM> is inclined with respect to a zero position, outputs a drive command to one or more servomotors <NUM> that adjust the inclination of the pillar <NUM> so that the inclination of the second cutting blade <NUM> returns to zero, i.e., that the pillar <NUM> returns to the zero position.

In other words, an inclination of zero (null inclination) is equivalent to the condition in which the pillar <NUM> (and therefore the second cutting blade <NUM>) is in the zero position.

The control unit <NUM> then controls the servomotors <NUM> so that the zero position of the pillar <NUM> is maintained in the face of inclinations on the ground.

At the same time, by processing the data as better described below, the first cutting blade <NUM> for cutting the upper portion of the hedge is adjusted by the control unit <NUM> to the desired height, so as to follow, for example, an inclined line having an angle of inclination with respect to the horizon line, the amplitude of which is indicated as "δ" (delta) in <FIG> is defined by the user.

It has to be noted that in <FIG> the arrows indicate the directions of advancement of the apparatus <NUM> on a ground profile <NUM>. Alternatively, the user could set a cut of the upper portion of the hedge parallel to the horizon line.

It has to be noted that, in <FIG> the ground profile <NUM> is represented in a simplified way with a regular line; however, it is unlikely to have such a ground profile but more realistically such a profile will be represented by a broken or curved line characterised by stretches of variable slope.

Once the cutting parameters have been set, the control unit <NUM>, during operation of the machine <NUM>, outputs a command signal to the motor dedicated to the sliding of the runner <NUM> so as to adjust the height of the first cutting blade <NUM> along the pillar <NUM>.

According to a preferred embodiment, the control unit <NUM>, in particular its software, regulates the drive of the motor dedicated to sliding the runner <NUM> on the basis of trigonometric operations.

With reference to <FIG>, when the apparatus <NUM> moves along a ground profile <NUM> according to a direction represented by the arrow in the figure, the advancement of the apparatus <NUM> can be imagined (and represented) as many small right-angled triangles whose hypotenuses constitute the ground profile <NUM>.

In <FIG>, in particular, two hypotenuses located respectively at a downhill and an uphill section of the ground profile <NUM> on which the apparatus <NUM> advances have been highlighted.

With reference to <FIG>, an example of a right-angled triangle is provided, constructed by trigonometric operations on a downhill section of ground profile <NUM>, in which the hypotenuse is denoted by the letter "c".

With reference to <FIG>, an example of a right-angled triangle is provided, constructed by trigonometric operations on an uphill section of ground profile <NUM>, in which the hypotenuse is denoted by the letter "c".

A cathetus "a" of the triangles in <FIG> represents the projection of the advancement range of the apparatus in a direction parallel to the horizon line, the other cathetus "b" of the triangles is the variation of ground level (orthogonal to the horizon line and therefore orthogonal to the cathetus "a") in the detected advancement range, the amplitude of the angle "β", opposite the cathetus "b", is provided by the inclination of the ground <NUM> detected by the inclinometer placed on the plate <NUM>.

The control unit <NUM>, by means of the software, detects the advancement range of the apparatus <NUM> from the pulses sent by the encoder; the detected advancement constitutes the hypotenuse "c" of the imaginary triangle while the inclination detected by the inclinometer constitutes the amplitude of the angle "β". The control unit <NUM> then processes the information received from the sensors and calculates the length of cathetus "b" opposite angle "β".

Therefore, the length of cathetus "b" will be calculated using the formula: <MAT>.

Considering furthermore that the amplitude of the angle "γ", opposite the hypotenuse "c", is always <NUM>°, since the angle "γ" represents the right angle between the two directions of the reference system considered, consisting of the horizon line and the vertical direction orthogonal thereto, the sine of the angle "γ" is always equal to <NUM>.

The above formula can therefore be simplified: <MAT>.

The value of cathetus "b" calculated as above therefore constitutes the height variation of the ground in the measured advancement range.

It has to be noted that the value of the cathetus "b" also constitutes the height variation of the first cutting blade <NUM> necessary to compensate for the height variation of the ground in the measured advancement range with respect to the starting point of the cutting blade <NUM> or to the position of the first cutting blade <NUM> resulting from the previous measurement.

Therefore, the control unit <NUM> will drive the motor that determines the sliding of the runner <NUM> to which the first cutting blade <NUM> is constrained in order to compensate for such height variation of the ground: the motor will move the runner <NUM> by an amount equal to the value of the cathetus "b".

It has to be noted that the value of the cathetus "b" can be a positive value (+) or a negative value (-), where the positive value corresponds to an increase in the height of the first cutting blade <NUM> above the ground and the negative value corresponds to a decrease in the height of the first cutting blade <NUM> above the ground.

If the desired cutting line is inclined with respect to the horizon line, a measurement of the change in ground level "b1" calculated using the same criterion as above, but replacing the angle "β" with the angle "δ", will be added to (or deducted from) the value of the cathetus "b": <MAT>.

The angle "δ" is the angle formed by the intersection of the horizon line with the upper cutting line of the desired hedge <NUM> (see <FIG>), where the amplitude of the angle "δ" is set by the user on the human-machine interface <NUM>. It has to be noted that in <FIG> the upper cutting line of the hedge <NUM> has been represented parallel to the simplified line representing the ground profile <NUM>, i.e. in the represented case the amplitude of the angle "δ" is equal to the amplitude of the angle "β".

However, the user can still set an angle amplitude value "δ" other than "β".

In this way, the apparatus <NUM> is able to compensate for depressions, bumps, disconnections and inclinations, which it encounters when advancing on an uneven ground profile (as schematically represented in <FIG>).

For example, the apparatus <NUM> shown in <FIG> and <FIG> and the apparatus <NUM> shown as an example in <FIG> can be moved manually by a user, or pulled/pushed manually, in particular by gripping the handlebars <NUM> and <NUM>. Note that the apparatus <NUM> shown in <FIG> differs in particular from the apparatus <NUM> shown in <FIG> and <FIG> due to the number of wheels used to move the apparatus: according to a person skilled in the art the further elements constituting the apparatus may be modified according to the teachings of the present invention. For example, with reference to <FIG>, the balance of the apparatus <NUM>, which comprises only a pair of wheels 2104a, is ensured by the user, who in particular, by gripping the handlebar <NUM>, acts as a third support point of the apparatus <NUM>. It has also to be noted that the wheels 2104a may be independent from each other: for example, in the case of steering the apparatus <NUM>, just one of the two wheels 2104a may be slowed down and/or braked in order to make a change of direction of the apparatus <NUM>, in particular to carry out a tight radius bend. Advantageously, this steering mode can be implemented in the case of three-wheel apparatus, where two wheels are steerable and a third wheel is free, i.e. its direction is not controlled.

Alternatively, the steering of the apparatus <NUM> may be carried out by applying a force to the handlebars <NUM> to achieve a twist.

Alternatively, the apparatus can be moved by an automatic guide system, e.g. it can run on a magnetic cable or magnetic track (typically underground), or on a physical guide, e.g. a steel cable, elevated above the ground, or on a track or monorail (see for example <FIG>), or it can move freely on wheels using an automatic guide system (GPS, optical system, proximity sensors, laser.

In some cases, particularly where the apparatus moves along a track or monorail, the wheels of the apparatus may be advantageously coupled or possibly replaced by pulleys or cylinders adapted to run along the track or monorail. In particular, the apparatus could comprise two or three wheels/pulleys/cylinders adapted to run along the rail or monorail and a wheel to run on a supporting rail or monorail; it has to be noted that the supporting rail or monorail could advantageously be replaced by a pre-existing structure in proximity to the hedge to be cut, for example a wall or fence.

With particular reference to <FIG>, an embodiment of the apparatus <NUM> capable of sliding along a monorail <NUM> associated with a wall <NUM> is shown (note that in <FIG> only a portion of the wall is shown), e.g. an enclosing wall of a property in the immediate vicinity of the hedge to be cut. In particular, the apparatus <NUM> may comprise a wheel (not visible in the figure) adapted to run along the monorail <NUM> and at least one wheel 3104a (the example embodiment shown in <FIG> depicts three of them) adapted to run along the wall <NUM>. Advantageously, the wheel adapted to run along the monorail <NUM> and the at least one wheel 3104a adapted to run along the wall <NUM> are arranged in such a way as to ensure the balance of the apparatus <NUM>. It has to be noted that the apparatus <NUM> shown in <FIG> differs in particular from apparatus <NUM> shown in <FIG> and <FIG> due to the movement system of the apparatus: according to a person skilled in the art the further elements constituting the apparatus may be modified according to the teachings of the present invention.

According to an alternative embodiment, the handlebar <NUM> may for example be a steering wheel and be twisted clockwise to steer in a first direction or anti-clockwise to steer in a second direction.

Finally, it is clear that the apparatus as conceived herein is susceptible to many modifications and variations, all falling within the present invention; furthermore, all the details are replaceable by technically equivalent elements. In practice, the materials used, as well as their dimensions, can be of any type according to the technical requirements.

According to another aspect, the object disclosed herein relates to a method of adjusting the height of a cutting blade.

The cutting blade is attached to a hedge trimmer that moves along a path over the ground on which the hedge to be cut is located and is height-adjustable in relation to the ground, in such a way as to vary its height with respect to the ground.

In particular, the trigonometric law used by the control unit to process the information is: <MAT> Wherein:.

Once the height variation of the ground has been calculated (step C), the control unit starts/shuts down the cutting blade drive motor or keeps the cutting blade drive motor started/shut down (step D) so that the height of the cutting blade in relation to the ground varies or not.

In particular, in step D, the control unit starts or keeps the cutting blade drive motor running if the difference between the height variation of the ground calculated in two subsequent advancement ranges is greater than a predefined tolerance and switches the cutting blade drive motor off or keeps it off if the difference between the height variation of the ground calculated in two subsequent advancement ranges is zero or less than a predefined tolerance.

For example, the control unit starts or keeps the engine running if the difference between the height variation of the ground calculated in two subsequent advancement ranges is greater than <NUM> in absolute value, while it stops or keeps the engine stopped if the difference between the height variation of the ground calculated in two subsequent advancement ranges is less than <NUM> in absolute value.

Therefore, if the calculated ground height is greater than <NUM> (in absolute value), the motor moves the cutting blade by an amount equal to the change in ground level, i.e. "b".

Claim 1:
Mobile hedge trimmer apparatus (<NUM>,<NUM>, <NUM>) comprising:
- a first portion (<NUM>), said first portion (<NUM>) acting as a mobile base adapted to rest on a ground and advance along a path and comprising a plate (<NUM>) and at least two wheels, preferably two pairs of wheels (104a, 104b),
- a second portion (<NUM>), said second portion (<NUM>) comprising a pillar (<NUM>) adapted to tilt on two axes (A and B) perpendicular to each other, said pillar (<NUM>) comprising a first cutting blade (<NUM>) and a second cutting blade (<NUM>), said first cutting blade (<NUM>) being adapted to slide along said pillar (<NUM>) and said second cutting blade (<NUM>) being integral with said pillar (<NUM>),
- a control unit (<NUM>), and
- sensors connected to said control unit (<NUM>);
wherein a control unit (<NUM>) is adapted to adjust the inclination of said pillar (<NUM>) on said axes (A and B) and/or the position of said first cutting blade (<NUM>) along said pillar (<NUM>), receiving information from said sensors,
wherein said sensors comprise at least one tool for measuring an inclination of the ground and/or of said pillar (<NUM>) and at least one movement sensor or advancement detector,
wherein said control unit (<NUM>) is adapted to receive information from said sensors repeatedly, in particular periodically, and to consequently adjust the inclination of said pillar (<NUM>) and/or the position of said first cutting blade (<NUM>) along said pillar (<NUM>).