Harvesters – Motorized harvester – With condition-responsive operation
Reexamination Certificate
1999-09-17
2001-11-27
Will, Thomas B. (Department: 3671)
Harvesters
Motorized harvester
With condition-responsive operation
C056SDIG007
Reexamination Certificate
active
06321515
ABSTRACT:
This invention relates to improvements to an autonomous lawn mower, more especially a multiple-cutting-head autonomous lawn mower.
The European patent EP-A-0 550 473 puts forward a low-power robotic mower traveling almost continuously over the surface to be mowed in random manner.
From the same above mentioned patent, a first improvement is known with respect to a purely random system by utilizing the measurement of the energy absorbed by the cutting head in order to determine whether or not the machine is in an already mown area. This enables the mower at one and the same time to adjust its progression speed in order to remain only a short time in an already mown area and on the other hand to modify its behavior when passing over a non-mown area (e.g. then to follow a spiral mowing path).
This invention puts forward additional improvements for the mowing efficiency of a robotic mower, in particular for mowing large surface areas, for example for golf courses or park surface areas.
One of the disadvantages associated with mowing devices designed for large surface areas such as utilized at present, consists in the utilization of a relatively powerful cutting system, the surface of the cutting head or heads having to be greater than for classic mowers for domestic use. The inertia of the cutting disk(s) or blade(s) is also greater. The safety in use of these devices therefore presents a problem, especially if a foreign body accidentally comes into contact with the cutting head(s). This safety problem also arises, and even more so, when robotic mowing devices are to be utilized for large surface areas.
According to a first aspect of the invention, a robotic mower is put forward which does not have or greatly reduces this inconvenience.
According to a second aspect of the invention, a guiding method for a robotic mower is put forward, more especially adapted to the robotic mower according to the invention.
Fundamentally two basic techniques exist for defining the route of a mobile autonomous robot, e.g. a robot for lawn mowing:
a systematic mowing technique by which the mower systematically mows the lawn, as a human being does with a classic mower, either by following a predetermined route, for example by concealing a guiding wire in the ground, or by utilizing a mapping and/or position finding system by means of markers;
a random route technique by which the robotic mower moves constantly in random manner on the surface area to be mowed without searching for a determined route.
The advantage of the latter technique is that it can be made naturally self-adapting which gives the system a very great strength. Its necessitates on the other hand a great number of passes in order to obtain a complete coverage of the surface area (3 passes guaranteeing 97% coverage). This hardly poses any problem in the case of a continuous technique (see European patent 0 550 473 relating to a possibly solar-powered robotic mower), but constitutes a handicap if a lawn is to be mowed occasionally and quickly with a robotic mower without predetermined guiding system.
All the elements mentioned but not described in detail in this specification are analogous or identical to those described in the above mentioned European patent 0 550 473, incorporated by reference into this specification.
According to a first aspect of the invention a robotic mowing device with several cutting heads is put forward.
More especially the mowing device has the following elements, taken separately or in any combination:
a mobile chassis comprising at least one driving wheel and on its lower side at least two juxtaposed cutting heads, preferably each connected to a preferably electric, independent motor
an electronic control system
an on-board computer
an electric power supply unit
a means for measuring the force provided by each cutting head, the aforesaid measurement being transmitted to the on-board computer
an algorithm stored in memory enabling the interaction of the advancement system of the device, the above mentioned force measurements and the on-board computer, means capable of enabling for example the searching for surface areas of grass to be cut;
a means for detecting the boundaries of the mowing surface area by measurement of a magnetic field or of the variation of a magnetic field emitted or caused by a laid-down or buried wire located at the aforesaid boundaries, and possibly
a means for detecting obstacles by analysis of relative movements of an upper plate of the device elastically integral to its chassis such as described in the European patent EP 0 550 473
an anti-theft device based on the measurement of the movement away from the ground and/or on a code peculiar to the user.
According to a first aspect of the invention the adoption of a machine with several cutting heads, preferably identical, is therefore provided. Thus two, three, four, five or more than five cutting heads can be provided, e.g. eight cutting heads, installed on one and the same mower chassis. According to an embodiment concretized at present, five cutting heads are provided. The cutting heads are preferably situated at the front of the chassis, which can measure e.g. from 60 cm to 2 m in width, their locations being at least offset one in relation to the other over the width of the chassis (direction perpendicular to movement). The power associated with each cutting head is generally situated between 10 and 90 watts, preferably between 15 and 60 watts, more preferentially between 20 and 50 watts. By way of example, the diameter of a cutting head can vary from 10 to 50 cm, a diameter of approximately 20 cm having proved advantageous.
The robotic mower with several cutting heads consists of a chassis driven by two driving wheels, similar to that described in the above mentioned European patent 0 550 473. The driving wheels will nevertheless advantageously have a considerably larger diameter, e.g. from 2 to 4 times greater, than the other wheels. At the front of the machine several independent cutting heads are mounted. According to an embodiment preferred at present each of the cutting heads is operated by its own electric motor.
These cutting heads are preferably flexibly mounted so that the ground irregularities can lift each cutting head independently. When such lifting occurs, the cutting power of the corresponding head could momentarily no longer be taken into account by the computer (parameter decoupling).
The cutting heads can be of the type described in the patent application PCT WO 96/242432.
The motors of each head can be independently operated and the measurement of the torque of each motor is transmitted to the on-board computer.
According to an embodiment of the invention, the cutting force of each head is constantly analyzed (e.g. several hundred times per second), in known manner, by the computer of the mower. When the machine partially overlaps a mown area and an unmown area, the result of the analysis of the forces on each cutting head enables the computer to situate the machine in relation to the boundary of the two areas and to position itself in consequence.
The on-board computer can thus control the route of the mower in order to make it approximately follow the demarcation between the two areas, resulting for example from the trace left by a previous pass of the robotic mower.
In order to mow a determined surface area, the device can be placed and actuated in any location of this surface area. The route can first be effected randomly until the computer detects a mown area/unmown area demarcation and actuates the above mentioned algorithm. The normal progression speed of the device can vary but is advantageously of approximately 1 m/sec (e.g. 2 to 5 km/h).
Alternatively, when the perimeter of the area to be mowed is defined by a wire, in which for example a low-frequency current flows such as described in the above mentioned patent EP-A-0 550 473, the above mentioned guiding technique based on the aforementioned demarcation can be combined with a technique linked to a systematic starting of the mowing process along the p
Petravick Meredith C.
Pillsbury & Winthrop LLP
Will Thomas B.
LandOfFree
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