Patent Description:
Robot lawnmowers provided with sensors which detect impact with animals, things or people, and with sensors for detecting the robot lawnmower itself, are known.

The impact sensors are necessary to stop the robot lawnmower in the event of impact and then ensure it changes travelling direction, while the lifting sensors serve to stop the rotation of the blade for safety reasons if the robot lawnmower is lifted during the working step.

In order to detect impact with animals, people or things, robot lawnmowers are commonly provided with a fluctuating cover which, in the event of impact, moves with respect to the base frame, informing the robot lawnmower by means of sensors and making it stop travelling to then change the direction thereof.

<CIT> describes means for detecting impact with obstacles of the movable cover type, with spring means associated with the base frame of the robot lawnmower.

<CIT> describes means for detecting impact with obstacles of the movable cover type, wherein the movement of the movable cover with respect to the base frame is signaled by magnets.

<CIT> discloses another similar robot lawnmower.

Disadvantageously, the obstacle impact detection means with a movable cover are costly, complex to make and keep efficient.

Robot lawnmowers with fixed cover (therefore not provided with fluctuating cover) which use the reading of the current on the driving motors to stop the travel in the event of impact, and as above, then change the direction of travel, are also known. The disadvantage of this solution is that the impact is significant and before stopping, the wheels tend to skid, ruining the yard; moreover, being significant, the force of impact is perceived as being unpleasant by people or animals.

In addition to collision sensors, <CIT> describes obstacle detection means of the visual type, i.e. by means of camera, and the use of ultrasound sensors and radar.

With regard to the lifting, the detection of the robot lawnmower occurs by means of sensors when the movable cover moves in vertical direction, thus allowing the sensors to intervene, which perceive the movement thereof in vertical direction with respect to the base frame.

Instead, in case of a fixed cover, the lifting sensor may intervene by means of a vertical movement of the axis of the front wheels, also provided with a specific sensor.

It is the object of the present invention to provide a robot lawnmower with a fixed cover provided with means for detecting obstacles, wherein the response of the driving wheels of the robot lawnmower is faster.

It is a further object of the present invention for the detection means to be affordable and simple to assemble on the robot lawnmower.

It is a further object again of the present invention for the detection means not to make more difficult the detection of the lifting of the robot lawnmower, which is useful for blocking the cutting blade for safety reasons.

According to the invention, said and further objects are achieved by a robot lawnmower comprising a base frame, a cover integral with the base frame, two driving wheels and at least one directional idler wheel, wherein each driving wheel is driven by an electric motor,
characterized in that.

Advantageously, the use of the elastic means allows a quick response to the bump and an effective damping effect: the robot lawnmower is not damaged and quickly resumes working in a different direction without skidding the wheels on the yard.

The absorbing means are simple to associate with the base frame and easily accessible from the outside for possible replacement.

The sensor is fixed to the base frame and well-protected by the cover integral with the base frame.

These and other features of the present invention will become more apparent from the following detailed description of practical embodiments thereof shown by way of non-limiting examples in the accompanying drawings, in which:.

A robot lawnmower <NUM> comprises a base frame <NUM>, a cover <NUM> integral with the base frame <NUM>, two driving wheels <NUM> and at least one directional idler wheel <NUM> (<FIG>).

Each driving wheel <NUM> is driven by an electric motor <NUM> by means of a gear <NUM> (<FIG>).

Motor <NUM> is fixed to a slide <NUM> by means of a bracket <NUM> to which the driving wheel <NUM> is rotatably associated by means of a hub <NUM> which is integral with bracket <NUM> and extends outwards from bracket <NUM>, as shown in <FIG>, for example.

Motor <NUM> therefore is integral with slide <NUM> and the driving wheel <NUM> is rotatably associated with bracket <NUM> by means of hub <NUM>.

The axis of hub <NUM> corresponds to the rotation axis X of the driving wheel <NUM> (<FIG>).

Slide <NUM> is adapted to slide along a guide <NUM> in the direction of motion, the direction of the motion axis Y, for example, wherein two pairs of springs <NUM> tend to keep slide <NUM> in a middle position of guide <NUM> (<FIG>, <FIG> and <FIG>).

The direction of the motion axis Y is orthogonal to the direction of the rotation axis X of the driving wheels <NUM> (<FIG>).

The rotation axes X and the motion axis Y identify an operating plane of the robot lawnmower <NUM> parallel to the ground on which the robot lawnmower <NUM> moves.

The motion axis Y coincides with the rectilinear direction of motion of the robot lawnmower <NUM> when the directional idler wheel <NUM> is aligned with the driving wheels <NUM>.

The motion of the robot lawnmower <NUM> may also occur along a curved trajectory at any point of which a component along the motion axis Y is always identifiable. The curved trajectory in any case is included in the operating plane of the robot lawnmower <NUM>.

In the embodiment shown, the sliding direction of slide <NUM> corresponds to the longitudinal direction of the robot lawnmower <NUM>, i.e., the direction of the motion axis Y, i.e., the direction of motion of the robot lawnmower <NUM> when the directional idler wheel <NUM> is oriented as the driving wheels <NUM> so that the robot lawnmower <NUM> moves forwards or backwards in rectilinear manner.

For example, the motion axis Y may be horizontal, i.e., the robot lawnmower <NUM> moves on a horizontal plane (ground).

Guide <NUM> is integral with the base frame <NUM> in the direction of the motion axis Y, while it may slide in the direction of a lifting axis Z by two pins <NUM> sliding along guides <NUM> between a high position and a low position (<FIG>). The high position preferably is the one of maximum height.

The lifting axis Z is orthogonal to the operating plane, i.e., to both the rotation axes X and the motion axis Y.

Usually, the lifting axis Z is vertical, i.e., the robot lawnmower <NUM> moves on a horizontal plane (ground).

The high position of the pins <NUM> corresponds to the working position of the robot lawnmower <NUM> in which a blade <NUM> is enabled to the cut motion, while the low position of the pins <NUM> corresponds to a lifting position of the robot lawnmower <NUM> in which blade <NUM> is not enabled to the cut motion for safety reasons.

The number of blades <NUM> may vary. For example, <FIG> shows four blades <NUM> which rotate integral with a conveniently driven cutting plate.

Motor <NUM> is fixed to bracket <NUM> so as to protrude above the base frame <NUM> towards a sensor <NUM> integral with the base frame <NUM> and adapted to detect the movement along the motion axis Y of motor <NUM> with respect to the base frame <NUM>, i.e., of slide <NUM> and the driving wheels <NUM> with respect to the base frame <NUM> (<FIG>, <FIG> and <FIG>).

Sensor <NUM> comprises a switch, is adapted to detect the movement of a magnet <NUM> integral with motor <NUM>, and controls the blocking and subsequent reversal of motion of the driving wheel <NUM> it is driving by means of a control unit of the robot lawnmower <NUM>.

A further sensor <NUM>, similar to sensor <NUM>, detects the movement along the lifting axis Z of the base frame <NUM> in case the robot lawnmower <NUM> is lifted, wherein a magnet <NUM> (<FIG>, <FIG>, <FIG>) integral with guide <NUM> interacts with said sensor <NUM> through a through hole <NUM> of guide <NUM> (<FIG>).

The movement along the lifting axis Z is also detected by a further sensor <NUM> again, similar to the sensors <NUM>, <NUM>, which is at the directional idler wheel <NUM> (<FIG>, <FIG>). More specifically, a pin <NUM>, integral with the directional idler wheel <NUM> along the lifting axis Z, is adapted to slide with respect to the base frame <NUM> from a high position and a low position. The high position preferably is the one of maximum height.

Similar to the positions defined for slide <NUM>, only if sensor <NUM> detects pin <NUM> in the high position, blade <NUM> is enabled for the cut motion (<FIG>). Sensor <NUM> detects magnet <NUM> in front of itself in such a position. The enabling of blade <NUM> is therefore controlled by two independent sensors <NUM>, <NUM> so as to increase the safety of the user.

Operatively, during the regular working motion, the robot lawnmower <NUM> provides for slide <NUM> to be in the middle of guide <NUM>, unless small oscillations comprised within a predefined threshold value in the control unit. Slide <NUM> and pin <NUM> of the directional idler wheel <NUM> are in the high position: blade <NUM> is enabled to the cut motion.

When the robot lawnmower <NUM> hits an obstacle and slide <NUM> moves from said middle position past said predefined threshold value, the control unit controls the stopping of the robot lawnmower <NUM> and the reversal of the motion of the driving wheels <NUM>. Following the bump, the control unit may also block blade <NUM> and restart it only after the reversal of motion.

Advantageously, the use of the springs <NUM> allows a quick response and an effective damping effect: the robot lawnmower <NUM> is not damaged and quickly resumes working in a different direction without skidding the wheels on the yard.

The configuration of the springs <NUM>, with slide <NUM> in the middle, allows a similar behavior in case of a front bump (<FIG>) and in case of a rear bump (<FIG>).

Guide <NUM> is simple to fix to the base frame <NUM> and the springs <NUM> are easily accessible from the outside for possible replacement.

The elastic means may also be internal because they do not require frequent adjustment and/or replacement, probably never during the life of the robot: the fact that they are internal gives them increased protection against damage by foreign bodies.

The means adapted to block blade <NUM> following lifting are simple to couple to the obstacle detection means.

The sensors <NUM>, <NUM>, <NUM> are fixed to the base frame <NUM>, well protected by cover <NUM>.

The sensors <NUM>, <NUM>, <NUM> are known movement sensors which are independently controlled by the control unit.

Alternatively, two pairs of springs <NUM> alone may be associated with each guide <NUM>. More generally, the presence of elastic means forcing slide <NUM> into the middle position is simply required.

Sensor <NUM> could be capable of detecting both a movement along the motion axis Y and a movement along the lifting axis Z, therefore rendering useless the sensors <NUM> and <NUM>, which in turn may be alternative.

The robot lawnmower <NUM> according to the present invention is simple to assemble, with obstacle impact detection means directly associated with the driving wheels <NUM>, in which the axis of the two driving wheels <NUM> is movable to translation with respect to the base frame <NUM>.

To detect the impact, therefore it is not necessary for cover <NUM> to be movable with respect to the base frame <NUM>: it is sufficient for the driving wheels <NUM> to be able to translate with respect to the base frame <NUM>.

The springs <NUM> serve a dual purpose: they define the blocking position of the driving wheels <NUM> and dampen the impact.

The components used for the detection means are commercially known and easy to find on the market. The position in which said components are assembled makes maintenance and possible replacement simple.

Alternatively, guide <NUM> may be oblique, i.e., slide <NUM> may slide according to a direction providing for both a component along the motion axis Y and a component along the lifting axis Z. There must always be the component along the motion axis Y so as to absorb the bump which has a prevailing component in the direction of the motion axis Y. Slide <NUM>, and therefore bracket <NUM>, is therefore in any case suitable to move in the direction of motion of the robot lawnmower <NUM>.

The elastic means are to keep slide <NUM> in a position of equilibrium, preferably but not exclusively a middle position of guide <NUM>.

According to a second embodiment shown in <FIG>, unlike the embodiment shown in <FIG>, the brackets <NUM> are again adapted to move with respect to the base frame <NUM> in the direction of motion of the robot lawnmower <NUM> but rotating around the lifting axis Z instead of translating in the direction of the motion axis Y (<FIG>).

More specifically, each bracket <NUM> is rotatably associated with frame <NUM> so as to rotate around the lifting axis Z (<FIG>).

A spring <NUM>, associated with bracket <NUM> in a pin <NUM>, is adapted to keep bracket <NUM> in equilibrium with respect to the base frame <NUM> in the absence of bumps (<FIG>).

A front or rear bump past a predetermined threshold forces spring <NUM> to allow the rotation of bracket <NUM> around the lifting axis Z, in one direction or the other based on the type of bump, front or rear (<FIG>).

Two sensors <NUM> adapted to detect the movement of a magnet <NUM> integral with bracket <NUM> of the driving wheel <NUM> are provided integral with frame <NUM>, for each driving wheel <NUM>.

The use of two separate sensors <NUM> allows the front bump and the rear bump to be distinguished.

Similar to the embodiment in <FIG>, also the second embodiment in <FIG> provides the sensors <NUM> and <NUM> for detecting the movement of the base frame <NUM>, and therefore of blade <NUM>, along the lifting axis Z.

Advantageously, in both embodiments, cover <NUM> always remains integral to the base frame <NUM>, while bracket <NUM> with motor <NUM> may move with respect to the base frame <NUM>, thus absorbing the bump.

Claim 1:
Robot lawnmower (<NUM>) comprising a base frame (<NUM>), a cover (<NUM>) integral with the base frame (<NUM>), two driving wheels (<NUM>) and at least one directional idler wheel (<NUM>), wherein each driving wheel (<NUM>) is driven by an electric motor (<NUM>),
wherein
each motor (<NUM>) is fixed to a bracket (<NUM>) to which the respective driving wheel (<NUM>) is rotatably fixed,
characterized in that
the robot lawnmower (<NUM>) comprises absorbing means (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) of a bump of the robot lawnmower (<NUM>), wherein the absorbing means (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) are adapted to allow the movement of the bracket (<NUM>) with respect to the base frame (<NUM>) in the case of a bump in the direction of motion of the robot lawnmower (<NUM>),
wherein the absorbing means (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) comprise elastic means (<NUM>, <NUM>) adapted to keep the bracket (<NUM>) in a position of equilibrium with respect to the base frame (<NUM>) in the absence of bumps,
said robot lawnmower (<NUM>) further comprising at least one sensor (<NUM>, <NUM>) fixed to the base frame (<NUM>) and adapted to detect said movement of the bracket (<NUM>) with respect to the base frame (<NUM>), and a control unit adapted to block and reverse the motion of the driving wheels (<NUM>) following the detection of said movement of the bracket (<NUM>) with respect to the base frame (<NUM>).