GB2295304A

GB2295304A - Steering control of lawn mowers

Info

Publication number: GB2295304A
Application number: GB9423845A
Authority: GB
Inventors: Craig Duncan Webster
Original assignee: Black and Decker Inc
Current assignee: Black and Decker Inc
Priority date: 1994-11-25
Filing date: 1994-11-25
Publication date: 1996-05-29
Anticipated expiration: 2014-11-25
Also published as: GB2334875A; GB9911981D0; GB9423845D0; GB2334875B; GB9911982D0; GB2334874B; GB2334874A; GB2295304B

Abstract

A lawn mower adapted for automatic and unattended operation, comprises; (a) first detection means 16 for detecting whether or not the mower is on grass; (b) second detection means for detecting the presence of obstacles in the path of the mower and (c) means responsive to said first and second detection means to determine the route of the mower. <IMAGE>

Description

Lawn Mower The present invention relates to a lawn mower, in particular a lawn mower which is adapted for automatic and unattended operation.

Numerous proposals have been made in the past, for automatic mowers which are said to be suitable for automatic and unattended operation. Most of these known proposed mowers are designed to operate only on a pre-prepared lawn, in which some mechanical guidance is provided, for example, rails buried in the lawn, or need to be pre-programmed to follow a specific path around the lawn.

It has also been proposed, for example in PCT Patent Application No. WO 92/04817 and in French Patent Application No. 2 645 700, to provide a mower whose route is determined in response to obstacles at the boundaries of the surface to be mowed, but such mowers require that the boundary of the surface to be mowed is provided with obstacles which the mowers detection system can detect, so that the boundaries of the surface to be mowed have to be specially prepared to be suitable for mowing by the mower.

It is an object of the present invention to provide a mower adapted for automatic and unattended operation in which the above disadvantages are reduced or substantially obviated.

The present invention provides a lawn mower adapted for automatic and unattended operation, which mower comprises (a) first detection means for detecting whether or not the mower is on grass, (b) second detection means for detecting the presence of obstacles in the path of the mower and (c) means responsive to said first and second detection means to determine the route of the mower.

The mower preferably further comprises means for detecting long grass, by which is meant grass longer than a predetermined length, and means for activating or deactivating a cutter mechanism of the mower in response to the long grass detector.

In a preferred embodiment the means for determining the route of the mower causes the mower to change direction either in the absence of grass or when the obstacle detection means detects an obstacle in the path of the mower.

The means for determining the route of the mower may also be responsive to the means for detecting long grass, and could respond to the absence of long grass by, for example, turning through 1800 when a change from long grass to short grass is detected, following a random path while searching for long grass and/or searching for long grass at a higher speed than the cutting speed.

In a particular preferred embodiment of a mower according to the invention the mower is powered by means of one or more solar cells or by a rechargeable battery. Where the mower is powered by a rechargeable battery, it is more preferably provided in combination with one or more solar cells which may be used to recharge the battery.

The one or more solar cells may be linked into the means for determining the route of the mower, so that the mower can search for sunlight in a similar way to that in which it searches for long grass.

The mower is preferably further provided with a monitoring system to monitor the state of charge of the battery and stop the mower to recharge when the charge is low.

The first detection means for detecting whether or not the mower is on grass may be of any suitable form, including mechanical sensing, optical sensing or electrical sensing or combinations of such sensing and may be adapted to detect the presence or absence of grass directly or by detecting the presence or absence of some marking system which has been selectively applied to the grass.

Where the first detection means for detecting whether or not the mower is on grass is adapted to detect grass indirectly, by means of a marking system applied to the grass, this can be achieved by any suitable marking method applied to the whole area of the grass, such as by distributing over the whole area of the grass a detectable metallic material such as metallic studs, ball bearings or ferrous filled plastic beads. The mower can be provided with a detector for detecting the presence or absence of the metallic marking material.

The second detection means for detecting the presence of obstacles in the path of the mower may comprise any suitable detection means, including mechanical or optical sensing means. A particularly suitable obstacle detection means is described and claimed in our co-pending European Patent Application No. 0 628 239.

The mower according to the invention preferably further comprises an appropriate security device to render the device inoperable if it should be removed from the operation site without authority. Examples of suitable security devices include a beacon, a location sensor or a time switch.

Two alternative embodiments of a lawn mower adapted for automatic and unattended operation will now be described with reference to the accompanying drawings, in which: Figure 1 is a general view of a first embodiment of the mower; Figure 2 is a longitudinal section of the mower of Figure 1; Figure 3 is an exploded view, with the upper casing removed, of the mower of Figure 1; Figure 4 is a view of an alternative embodiment of a grass detection means and Figure 5 is a block diagram showing a start up sequence for the mower.

As shown in Figure 1, the mower shown generally at 2, comprises a housing 4 equipped with two independently driven wheels 6 and a second pair of wheels 8. The wheels 6 are spiked to improve aeration and to reduce damage to and compaction of the grass resulting from constant traversing by the mower. Solar cells 10 are located on the housing 4 and a bumper 12 is located at a first end of the housing 4.

A detection mechanism shown generally at 14 comprises an array of grass detection sensors 16, pivoted adjacent said first end of the housing 4 about pivot points 18, each sensor 16 comprising a pair of arms 20,22 joined at the pivot point 18. Each of the arms 20 depends from the pivot point 18 and is aligned with a corresponding aperture 24 in an array of apertures formed in the lower rim of said first end of the housing 4.

Each of the second arms 22 of the pair of arms forming the sensor 16 is set at approximately 90 to the first arm 20. A light source 28 is provided, which light source generates a light beam 30 which is obstructed by each of the second arms 22, when the corresponding sensor 16 is in the rest position. A detector (not shown) is provided to detect whether or not the light beam 28 is broken. The array of sensors 16 may be adapted to pivot independently or together.

The mower 2 is further provided with a second mechanism for grass detection, shown generally at 34. This second mechanism is for long grass detection and its operation will be described in more detail below.

A height of cut adjustment mechanism 36 including an operating lever 38 is provided, the operating lever 38 projecting through an aperture 40 provided in the housing 4.

The mower 2 is further provided with reciprocating cutters 42 driven by a motor 44, which is powered by a rechargeable battery 46. Further motors 48, 50 drive the driven wheels 6.

The solar cells 10 are used to recharge the battery 46 which not only drives the cutters 42 and wheels 6 but also provides the power for the light source 28 and the control systems for the mower.

In operation, when the mower is placed in a particular location and switched on by the operator, a start up program is instigated, comprising the stages shown in the block diagram in Figure 5.

Signals received from the detection mechanism 14 are used to determine the path of the mower 2. When the first arms 20 of the sensors 16 contact grass, they are deflected and pivot from their rest position to a detecting position.

As the second arms 22 are fixed relative to the first arms 20, the second arms are similarly pivoted from their rest position so that they are no longer aligned with the light beam 30. The detector 32 sends a signal to the control mechanism for the mower that the light beam is no longer interrupted and the control mechanism interprets this to be due to the presence of grass and proceeds accordingly.

When the mower has travelled a sufficient distance so that it has reached the edge of the area of grass on which it has been placed, the arms 20 of the sensors 16 pivot from their grass detecting position back to the rest position.

Since, as has been described above, the second arms 22 are fixed relative to the first arms 20, the second arms are similarly pivoted back to their rest position so that the apertures 26 are no longer aligned with the light beam 30.

The detector 32 sends a signal to the control mechanism for the mower that the light beam is now interrupted and the control mechanism interprets this to be due to the absence of grass and proceeds accordingly.

As has been mentioned above, the mower also comprises a second detection mechanism 34 for the detection of the presence of long grass. This detection mechanism 34 is similar to the grass detection mechanism 14, but is designed to send a positive signal to the control mechanism for the mower when grass longer than a predetermined length is encountered. As shown in Figure 3, a light source is focused on a detector. When the light beam is interrupted by grass longer than the predetermined length, a positive signal is sent to the control mechanism for the mower which responds by activating the cutters 42.

In the alternative embodiment shown in Figure 4, the grass detection mechanism 14 of the first embodiment is replaced by a pair of parallel dependent plates 402, 404 with an air gap 406 between the two plates. Together with the air gap 406, the plates 402, 404 form a capacitor, the capacitance of which changes when grass is present between the plates.

In a further alternative embodiment of the mower according to the invention, the first detection means for detecting whether or not the mower is on grass may be arranged so that deflection of a single sensor from its rest position to its detecting position will indicate to the control unit for the mower that it is on a grass surface.

This can be achieved in a number of ways, for example by arranging the sensors so that the light beam is uninterrupted when all of the sensors are in the rest position and interrupted when at least one sensor is deflected into the detecting position, or by providing each of the sensors with its own light source and associated beam detector.

Claims

Claims

1A lawn mower adapted for automatic and unattended operation, which mower comprises; (a) first detection means for detecting whether or not the mower is on grass; (b) second detection means for detecting the presence of obstacles in the path of the mower and (c) means responsive to said first and second detection means to determine the route of the mower.
2 A mower according to claim 1 characterised in that it further comprises means for detecting long grass, and means for activating or deactivating the cutter mechanism of the mower in response to the long grass detector.
3 A mower according to claim 1 or claim 2 characterised in that the means responsive to the first detection means causes the mower to change direction in the absence of grass.
4 A mower according to any of claims 1 to 3 characterised in that the means responsive to the second detection means causes the mower to change direction in response to an obstacle in the path of the mower.
5 A mower according to any of claims 2 to 4 characterised in that the means responsive to the first and second detection means is also responsive to the means for detecting long grass.
6 A mower according to any of claims 1 to 5 characterised in that the mower further comprises a rechargeable battery.
7 A mower according to any of claims 1 to 6 characterised in that the mower further comprises one or more solar cells.
8 A mower according to claim 7 characterised in that the one or more solar cells are used to power the mower.
9 A mower according to claim 7 characterised in that the one or more solar cells are used to recharge the battery.
10 A mower according to any of claims 7 to 9 characterised in that the means for determining the route of the mower is also responsive to the one or more solar cells.
11 A mower according to any of claims 6 to 10 characterised in that the mower further comprises a monitoring system for monitoring the state of charge of the battery.
12 A lawn mower adapted for automatic and unattended operation substantially as herein described with reference to the accompanying drawings.