Patent Description:
Robot lawnmowers provided with sensors which detect impact with animals, things or people, and with lifting sensors of 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 and 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.

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.

Another type of robot lawnmower with a flexible transmission is known from <CIT>.

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,
wherein.

Advantageously, the use of the elastic means allows a quick response 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 configuration of the absorbing means allows a similar behavior both in the event of a front bump and in the event of a rear bump.

The robot lawnmower according to the present invention is simple to assemble, with obstacle impact detection means directly associated with the motor block, in which the axis of the driving wheels is fixed at the translation in the direction of motion with respect to the base frame.

To detect the impact therefore, it is not necessary for the cover to be movable with respect to the base frame: it is sufficient for the motor block to be rotatable with respect to the bracket.

The elastic means serve a dual purpose: they control the blocking of the driving wheels and dampen impact.

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 (not shown) associated 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 a respective motor <NUM> of the electric type by means of a pinion <NUM> which meshes with a ring gear <NUM> of the driving wheel <NUM> (<FIG>).

Motor <NUM> comprises a motor block <NUM> rotatably fixed to a bracket <NUM>.

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

The base frame <NUM>, which provides a compartment <NUM> for a cutting plate <NUM>, comprises one or more cutting blades.

The axis of hub <NUM> corresponds to the rotation axis X2 of the driving wheel <NUM>, in which the driving wheel <NUM> is rotatably mounted on hub <NUM> by means of a bearing <NUM> (<FIG>).

The motor block <NUM> is adapted to rotate around a rotation axis X1 which preferably corresponds to the rotation axis of pinion <NUM>.

Preferably, the rotation axis X1 is parallel to the rotation axis X2 of the driving wheel <NUM> but is separate therefrom, i.e., motor <NUM> is not aligned with the driving wheel <NUM>, i.e., motor <NUM> is off-axis with respect to the driving wheel <NUM>.

Pinion <NUM> naturally is adapted to rotate with respect to the motor block <NUM> which is kept in equilibrium in a working position by a spring <NUM> which preferably is placed around a portion of the motor block <NUM> closest to bracket <NUM>.

Working position means a position of the motor block <NUM> which allows the movement and cutting of the robot lawnmower <NUM>.

The motor block <NUM> comprises two pins <NUM> adapted to slide in two curved guides <NUM> of bracket <NUM> (<FIG>).

When the motor block <NUM> is in said working position, the pins <NUM> are in a middle position in the curved guides <NUM>.

Preferably, bracket <NUM> extends upwards so that motor <NUM> can be mounted in a high position of bracket <NUM>, extending inwards, above the base frame <NUM>, in particular above compartment <NUM>.

The driving wheel <NUM>, driven in rotation by pinion <NUM> which meshes with the ring gear <NUM>, rotates on hub <NUM> which is fixed to bracket <NUM>. Alternatively, hub <NUM> may be integral with the driving wheel <NUM> and rotate with respect to bracket <NUM>, i.e., the position of the bearing <NUM> may vary, motor <NUM> in any case remaining off-axis.

Advantageously, the sizes of compartment <NUM> in which the cutting plate <NUM> is accommodated are not affected by the presence of the motors <NUM> adapted to drive the driving wheels <NUM>.

Therefore, the robot lawnmower <NUM> may be designed with the cutting plate <NUM> centered between the driving wheels <NUM>, with an optimal distribution of the weight and reduced longitudinal sizes of the robot lawnmower <NUM>.

The motion of the robot lawnmower <NUM> may occur along a rectilinear trajectory, for example, along a motion axis Y (<FIG>), or along a curved trajectory along every point of which a component may in any case always be identifiable along the motion axis Y.

The direction of the motion axis Y is orthogonal to the direction of the rotation axis X2 of the driving wheels <NUM>.

The rotation axes X2 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 curved trajectory in any case is included in the operating plane of the robot lawnmower <NUM>.

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>.

In the embodiment shown, the direction of the motion axis Y corresponds to the longitudinal direction of the robot lawnmower <NUM>, 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).

Bracket <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 (<FIG>, <FIG>) between a high position and a low position. The high position preferably is the one with maximum height.

With particular reference to <FIG>, bracket <NUM> comprises a C-shaped profile <NUM> and a body <NUM> extending in the direction of the lifting axis Z between two ends of the C-shaped profile <NUM>.

Body <NUM> is slidably fixed in the direction of the lifting axis Z at a block <NUM> which is integral with frame <NUM>.

Bracket <NUM> may slide with respect to frame <NUM> in the direction of the lifting axis Z by virtue of said sliding fixing of body <NUM> with block <NUM>.

Bracket <NUM> therefore is movable between said high position and low position with respect to block <NUM>, i.e., with respect to frame <NUM>.

The lifting axis Z is orthogonal to the operating plane, i.e., to both the rotation axes X2 and to 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 bracket <NUM> (<FIG>) corresponds to the working position of the robot lawnmower <NUM> in which a blade is enabled to the cut motion, while the low position of bracket <NUM> corresponds to a lifting position of the robot lawnmower <NUM> in which the blade is not enabled to the cut motion for safety reasons.

The motor block <NUM> is rotatably fixed to bracket <NUM> so as to protrude above the base frame <NUM> towards a sensor <NUM> (<FIG>) integral with the base frame <NUM> and adapted to detect the rotation of the motor block <NUM> around the rotation axis X1 with respect to bracket <NUM> (<FIG>, <FIG>, <FIG>).

Sensor <NUM> comprises a switch, is adapted to detect the movement of a magnet <NUM> integral with the motor block <NUM> and controls the blocking and subsequent reversal of motion of the driving wheel <NUM> that 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 the event the robot lawnmower <NUM> is lifted, in which a magnet <NUM> (<FIG>, <FIG>) integral with bracket <NUM> interacts with said sensor <NUM> integral with the base frame <NUM>. For example, sensor <NUM> is fixed above block <NUM> and magnet <NUM> is fixed to an upper end of the C-shaped profile <NUM> of bracket <NUM>.

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>). 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> between a high position and a low position. The high position preferably is the one with maximum height.

Similar to the positions defined for bracket <NUM>, only if sensor <NUM> detects pin <NUM> in the high position is blade enabled for the cut motion. Sensor <NUM> detects magnet <NUM> in front of itself in such a position. The enabling of the blade 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 the pins <NUM> of the motor block <NUM> to be in the middle position of the curved guides <NUM> (<FIG>), except for small oscillations comprised within a predefined threshold value in the control unit. Bracket <NUM> and pin <NUM> of the directional idler wheel <NUM> are in the high position: the blade is enabled for the cut motion.

When the robot lawnmower <NUM> hits an obstacle and the motor block <NUM> rotates around the rotation axis X1 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 the blade and restart it only after the reversal of motion.

Following the bump, the pins <NUM> move from said middle position of the curved guides <NUM> to a side position of the curved guides <NUM>.

<FIG>, <FIG> and <FIG> show the case in which the motor block <NUM> rotates in clockwise direction, i.e., in the event of a rear bump. The rotation is inverse in the event of a front bump.

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 the pins <NUM> in the middle of the curved guides <NUM> in working position, allows a similar behavior both in the event of a front bump and in the event of a rear bump.

The motor block <NUM> is simple to fix to bracket <NUM> and the springs <NUM> are easily accessible from the outside for possible replacement.

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

The means adapted to block the blade 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 the cover.

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

Sensor <NUM> could be capable of also detecting 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 motor block <NUM>, in which the axis of the driving wheels <NUM> is fixed at the translation in the direction of the motion axis Y with respect to the base frame <NUM>.

To detect the impact therefore, it is not necessary for the cover to be movable with respect to the base frame <NUM>: it is sufficient for the motor block <NUM> to be rotatable with respect to bracket <NUM>, in particular around a rotation axis X1 parallel to the rotation axis X2 of the driving wheels <NUM>.

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

The springs <NUM>, together with the pins <NUM> and the curved guides <NUM>, constitute absorbing means of the bump of the robot lawnmower <NUM> with an obstacle.

The bump absorbing means, together with means adapted to allow the lifting associated with bracket <NUM>, form a motor unit <NUM> shown in <FIG>.

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.

The elastic means have to keep the motor block <NUM> in a position of equilibrium, preferably but not exclusively with the pins <NUM> in a middle position of the curved guides <NUM>.

Claim 1:
Robot lawnmower (<NUM>) comprising a base frame (<NUM>), a cover 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>),
characterized in that
each motor (<NUM>) comprises a motor block (<NUM>) rotatably fixed to a bracket (<NUM>) to which the respective driving wheel (<NUM>) is rotatably fixed,
wherein the robot lawnmower (<NUM>) comprises absorbing means (<NUM>, <NUM>, <NUM>) of a bump of the robot lawnmower (<NUM>), wherein the absorbing means (<NUM>, <NUM>, <NUM>) are adapted to allow the rotation of the motor block (<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>) comprise elastic means (<NUM>) adapted to keep the motor block (<NUM>) in a position of equilibrium with respect to the bracket (<NUM>) in the absence of bumps,
said robot lawnmower (<NUM>) further comprising at least one sensor (<NUM>) fixed to the base frame (<NUM>) and adapted to detect said rotation of the motor block (<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 rotation of the motor block (<NUM>) with respect to the base frame (<NUM>).