GB2334874A

GB2334874A - Steering control of lawn mowers

Info

Publication number: GB2334874A
Application number: GB9911981A
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: 1999-09-08
Anticipated expiration: 2014-11-25
Also published as: GB9911982D0; GB2334875A; GB2334875B; GB2295304B; GB9911981D0; GB2295304A; GB9423845D0; GB2334874B

Abstract

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 a grass surface by detecting the presence of grass directly, the first detection means comprising a pair of parallel dependent plates 402, 404 with an air gap 406 between the two plates and which form a capacitor; a second detection means for detecting the presence of obstacles in the path of the mower; and means responsive to said first and second detection means to determine the route of the mower.

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 preprogrammed 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.

Accordingly, there is provided 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 a grass surface by detecting the presence of grass directly, the first detection means comprising a pair of parallel dependent plates with an air gap between the two plates and which form a capacitor; (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 detection.

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 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.

An embodiment 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 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 the first 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 a pair of parallel dependent plates 402, 404 with an air gap 406 between the two plates (as best shown in Fig. 4). 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.

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 4.

Signals received from the detection mechanism 14 are used to determine the path of the mower 2.

As has been mentioned above, the mower also comprises a second detection mechanism 34 for the detection of the presence of long grass. It 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.

Claims

CLAIMS 1. 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 a grass surface by detecting the presence of grass directly, the first detection means comprising a pair of parallel dependent plates with an air gap between the two plates and which form a capacitor; 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 de-activating the cutter mechanism of the mower in response to the long grass detector.
3. A mower according to Claim 2 characterised in that the means responsive to the first and second detection means is also responsive to the means for detecting long grass.
4. A mower according to any one of Claims 1 to 3 characterised in that the means responsive to the first detection means causes the mower to change direction in the absence of grass.
5. A mower according to any of Claims 1 to 4 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.
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 mower adapted for automatic and unattended operation substantially as claimed in claim 1 and as herein described with reference to the accompanying drawings.

12. A mower adapted for automatic and unattended operation substantially as herein described with reference to the accompanying drawings.

Amendments to the claims have been filed as follows 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 I 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.