GB2170085A - Improvements in ground treatment vehicles - Google Patents

Abstract

A ground treatment vehicle, especially a driven lawnmower, 1, is capable of substantially untended operation. A control means, 6, comprises a cam, 9, which is a representation of the edges of a pre-determined area of ground, eg a lawn, and an elongate steering cord, 18, controlled by the shape of the cam, provides steering instructions to a steering wheel, 2, on the mower. <IMAGE>

Description

SPECIFICATION Improvements in ground treatment vehicles This invention concerns improvements in ground treatment vehicles, more especially it concerns such vehicles capable of substantially untended operation.

It has been desired for many years to have a vehicle such as a lawnmower or a tractor capable of operating over an area of ground without constant human attention. Thus, for example, UK Patent Specification No 151,916 describes a tractor which is intended to work outwards in a spiral from an anchor stake in the middle of a field, by gradually unwinding a cable from the stake. However, it is believed that known arrangements do not provide for untended operation into the corners of a normal field.

The present invention now provides a ground treatment vehicle for treating an area of ground, comprising a driven ground treatment vehicle, an elongate steering link attachable to said vehicle, and control means capable of controlling the steering link so that said vehicle is constrained to move within a pre-determined area of ground, said control means comprising an adjustable memory device capable of being adjusted to retain a memory of desired constraints corresponding to the pre-determined area of ground.

The ground treatment vehicle may be one of a wide variety of vehicles including agricultural, horticultural and domestic treatment vehicles such as ploughs, cultivators, rakes, spreaders for solid or fluid substances including irrigation water, brushes, vacuum and other cleaners, polishers and, especially, lawnmowers. Although the lawn.mower may be a hover mower, it is preferred that the lawnmower is a cylinder or rotary mower having one or more drive wheels or rollers contacting the ground. The lawnmower may have a steering mechanism, including one or more steering wheels, to which the elongate steering link may be attached.

Preferably, the steering link is a cord, cable or the like having biasing means, which biasing means may be provided by spring or the inbuilt elasticity of a suitable cord. The steering link may comprise two cords or cables adapted to provide accurate steering of the vehicle, and may form or be in addition to an electricity supply cable if the vehicle is electrically powered. The steering link may, in a further embodiment act to carry electric or other signals transferring steering instructions derived from the memory device to an on-board steering motor, switch, solenoid, or the like.

The control means may be adapted to be positioned centrally, to one side or outside the area of ground. It may provide for an initially largely undirected movement of the vehicle. For example, the control means may allow the vehicle to describe an initial spiral, and then cause constraints to be applied as the vehicle approaches the edges of the area, to prevent the vehicle from moving outside the area. In the case of a lawnmower, the mower may cut an initial spiral outwards from the control means until the mower approaches the edge of the lawn whereupon the steering link is caused by the memory device to limit otuward movement of the mower in the appropriate places. Of course, the mower may start at the edge of the lawn, and cut inwards, or may cut both inwards and outwards.

A preferred adjustable memory device is a mechanical device providing continuous or semi-continuous representations of the edges of the area, or providing indicia signifying desired turning points for the vehicle. Conveniently, the device is a cam, co-operating with a cam follower. The cam may be a conventional cam on a spindle, a plate or board cut in a direct or reverse representation of the edges of the area of ground, which plate or board is attached to the control means. The cam follower suitably, directly or indirectly, transfers steering instructions to the steering link. Also, the cam follower may enlarge, to a greater or lesser extent, the shape of the cam, by known mechanical means.

Desirably, the steering link is fed from a supply, which is preferably a reel or a drum, controlled by the cam and cam follower, to enable the vehicle to describe an initial spiral path and then a path incorporating the necessary constraints.

The invention will now be described with reference to the accompanying drawings, in which Figure 1 shows a plan view of one embodiment of the invention, applied to a domestic lawnmower, and Figure 2 shows a side view of the control means of the embodiment of Figure 1.

Referring to the Figures, a driven motor lawnmower is indicated by 1. The mower has forward extension arms carrying a steerable wheel, 2, which is linked to a steering arm, 3, mounted on a pivot, 4, and the arm is biased outwards by a coil spring, 5. It may be desirable to have some form of stop (not shown) in order to limit the movement of the steerable wheel.

A control means is generally indicated by 6, and has a base, 7, which may be located in a lawn by means of tines or spikes, 8. Fixed to the base is a cam, 9, which is a reverse representation of the shape of a complex lawn. A spindle, 10, extends through the base and cam, and on the spindle is rotatably fitted a bar, 11, and hinged to the bar at 12 is a control bar, 13. The bar 11 may be telescopic. The control bar 13 carries a rotatable cam follower, 14, having a retaining shoulder, 15. A coil spring, 16, is provided linking the control bar to bar 11, and acts to prevent uneven control, especially immediately after the cam follower has passed a wide part of the cam.

The bar 11 carries at its end remote from the mower, a rotatable steering cord reel, 17, onto which is wound a steering cord, 18, which extends to the steering arm 3 on the mower. The reel 17 is fixed to a smaller diameter reel, 19, on which is wound a control cord, 20, fixed at its other end to the control bar 13, so that movement of the control bar caused by the cam follower moving around the cam, results in an emphasised movement of the steering cord, and the corresponding steering of the mower. The steering cord is extendible from the control means to the driven vehicle at any part of the area of ground.

The mower is attached by a resilient anchor line, 21, formed in this embodiment by a spring, 22, and a cord portion, 23, which cord is passed through an eye, 24, on the end of bar 11, to an anchor cord drum, 25, rotatably mounted on the spindle. Movement of the mower acts to rotate the bar 11, and under the tension of steering cord 18, steering arm 3 is pulled inwards, so that the mower turns around the spindle 10. The cords 18 and 23 are unwound from reels 17 and 25, and the mower is allowed to cut a spiral outwards rather than merely a circle. As real 17 rotates to unwind cord 18, the smaller diameter reel 19 acts to wind in control cord 20 and pull in control bar 13. As the mower approaches the edge of the lawn, the cam follower contacts the cam, moving the control bar 13. The movement of the control bar then modifies the tension in the steering cord 18, and steering signals are transmitted to steering arm 3. Optionally, a stabilising cord, 26, is run from a small diameter reel, 27, mounted on top of reel 25, over a freely rotating pully, 28, on the bar 11 to control bar 13.

Reel 25 is preferably kept taut by a spring, 29.

The device described above has been successfully used to cut domestic lawns automatically.

Many variants of the invention operating in essentially the same manner but using equivalent means may be considered and are within the scope of the present invention.

Claims (11)

1. A ground treatment vehicle for treating an area of ground, comprising a driven ground treatment vehicle, an elongate steering link attachable to said vehicle, and control means capable of controlling the steering link so that said vehicle is constrained to move within a pre-determined area of ground, said control means comprising an adjustable memory device capable of being adjusted to retain a memory of desired constraints corresponding to the pre- determined area of ground.

2. A vehicle according to claim 1, wherein the driven vehicle is a lawnmower.

3. A vehicle according to claim 1 or 2, wherein the driven vehicle has a steering mechanism to which the steering link is attachable.

4. A vehicle according to claim 1, 2 or 3, wherein the steering link is one or two cords or cables extendible from the control means to the driven vehicle at any part of the area of ground.

5. A vehicle according to any one of the preceding claims, wherein the control means is positionable within or outside the area of ground.

6. A vehicle according to any one of the preceding claims, wherein the memory device is a cam.

7. A vehicle according to claim 6, wherein the cam is a plate or board cut in a direct or reverse representation of the edges of the pre-determined area.

8. A vehicle according to claim 6 or 7, wherein the cam co-operates with a cam follower in an arrangement transferring steering instructions to the steering link.

9. A vehicle according to claim 8, wherein the steering link comprises a cable or cord extending from a reel to the driven vehicle, the tension of the cable or cord being at least partially controlled by the position of the cam follower.

10. A vehicle according to any one of the preceding claims, additionally comprising an anchor cord or cable extending from the control means to the driven vehicle.

11. A vehicle according to claim 1, substantially as hereinbefore described with reference to the accompanying drawings.