WO2013038121A1

WO2013038121A1 - Lawnmowers

Info

Publication number: WO2013038121A1
Application number: PCT/GB2011/051707
Authority: WO
Inventors: Ian Zetterstrom Smith; Roger Thomas
Original assignee: Husqvarna Uk Limited
Priority date: 2011-09-13
Filing date: 2011-09-13
Publication date: 2013-03-21
Also published as: CN103796503A; CN103796503B; GB201403208D0; GB2513452A; GB2513452B

Abstract

A lawnmower, typically a hover mower, comprising: a housing (1) open on a bottom surface (2) thereof and defining a cutting chamber (3) and a lift chamber (4) on the bottom surface; a cutting element (6) in the cutting chamber; and a lift-generating member (8) in the lift chamber (4), in which the cutting element (6) and the lift- generating member (8) are mounted for rotation about generally vertical axes (7, 9) which are generally perpendicular to the bottom surface (2).

Description

LAWNMOWERS

This invention relates to lawnmowers. Hover mowers are well known in the prior art. Typically, they comprise a housing that defines an hover chamber open on a bottom surface, in which operates a cutting blade that rotates about a vertical axis and an impeller which generates a cushion of pressurised air which is forced downwards to generate lift. It has been proposed to provide hover mowers with separate chambers for the generation of lift and for the cutting of grass; in the United Kingdom patent application published as GB 2 318 966, this was done in order to aid in grass collection. In this example, a rotary blade is provided in a cutting chamber at the front of the lawnmower and a lift chamber is provided at the rear of the lawnmower with pressurised air by means of a system of ducting. The impeller that is the source of the pressurised air is directly driven off the motor shaft and so must be driven at the speed of operation of the motor. The motor is provided over the lift chamber, surrounded by a grass box. According to a first aspect of the invention, there is provided a lawnmower comprising: a housing open on a bottom surface thereof and defining a cutting chamber and a lift chamber on the bottom surface; a cutting element in the cutting chamber; and a lift-generating member in the lift chamber, in which the cutting element and the lift-generating member are mounted for rotation about generally vertical axes which are generally perpendicular to the bottom surface.

This represents an improvement over prior art two-chamber hover mowers in that the lift-generating member is placed in the lift chamber, rather than relying upon ducted airflow. Placing the lift-generating member in the lift chamber allows a larger, quieter lift-generating member to be used than would otherwise be the case and allows a larger selection of lift-generating members to be used, therefore allowing the lift- generating member to be selected from a wider group, allowing the lift-generating member to be optimised for flow, speed and noise, as the lift chamber can be made of a suitable size. The lift-generating member may comprise an impeller, such as a mixed-flow fan. Such fans have been found to be quieter than prior art fans.

Typically, the lawnmower will comprise a motor having an output shaft. The lawnmower will preferably comprise a lift transmission having an input rotatable about a first lift transmission axis and an output rotatable about a second lift transmission axis, the first lift transmission and second lift transmission axes being spaced from one another, the input being coupled to the output so as to transmit rotation of the input to rotate the output, the input being coupled to the output shaft of the motor and the output being coupled to the lift-generating member. Thus, this allows the lift-generating member to be spaced from the motor.

Similarly, the lawnmower may comprise a cutting transmission, having an input rotatable about a first cutting transmission axis and an output rotatable about a second cutting transmission axis, the first cutting transmission and second cutting transmission axes being spaced from one another, the input being coupled to the output so as to transmit rotation of the input to rotate the output, the input being coupled to the output shaft of the motor and the output being coupled to the cutting member.

At least two of the first and second cutting transmission axes and the first and second lift transmission axes may be parallel. Typically, the first cutting transmission axis and the first lift transmission axis will be coincident, and coincident with the output shaft of the motor. The second cutting transmission axis may be coincident with the vertical axis of the cutting member and the second lift transmission axis may be coincident with the vertical axis of the lift-generating member.

By having the lift-generating and cutting members both driven by their respective transmissions, the motor, the lift-generating member, cutting member and the motor can be spaced where desired in the housing. There is no longer any need to have the motor, for example, co-axial with the lift-generating member, and so the relatively heavy motor can be placed where desired in order to achieve a desired mass distribution. This means, for example, that the motor can be moved forwards as compared with prior art lawnmowers, allowing a larger grass box to be provided. As such, the motor may be provided closer to the centre of extent of the housing in a horizontal plane than to the edge of the extent of the housing. Typically, the motor will not be surrounded by any part of a grass box of the lawnmower.

The cutting element may be mounted on a cantilever member, the cantilever member being fixed to the housing at a mounting point distal to the cutting element; flexure of at least one of the housing and the cantilever member allowing the cutting member to move generally along its vertical axis relative to the housing.

Thus, this provides a convenient way of allowing a height adjustment for the cutting element without the user having to re-fix the cutting element. Furthermore, because the lift-generating member can be mounted around the mounting point, there is no need for the lift-generating member to move with the cutting element; with prior art systems where the lift-generating member is coaxially mounted with the cutting element, moving the shaft on which the cutting element is mounted would necessarily move the lift-generating member. Doing so is likely to impair the function of the lift- generating member, as they will generally be tailored to work in a certain position, and with certain clearances, relative to the housing of the lawnmower.

The movement of the cutting member generally along its vertical axis will typically not be entirely linear, but will involve a component of pivotal motion about a point near to the mounting point. However, because the mounting point is distal from the cutting element, the movement will typically be approximately linear.

The lawnmower may further comprise an adjuster, which drives flexure of at least one of the cantilever and the housing so as to move the cutting element. The adjuster may be manipulable by a user with the bottom surface lowermost. Thus, the user does not have to turn the lawnmower over when adjusting the cutting height. The adjuster may comprise a cranked bar having a cranked portion which works in a slot in the cantilever member, rotation of the cranked bar causing movement of the cantilever relative to the housing. The lawnmower may further comprise a locking mechanism whereby the position of the cantilever relative to the housing can be fixed, thereby fixing the position of the cutting member relative to the housing along its vertical axis. The adjuster may comprise the locking mechanism, which may comprise a lever fixed to the cranked bar, typically which is biased against the housing. Typically, the adjuster will have a plurality of discrete positions at which the adjuster locks the position of the cutting member along its vertical axis; the discrete positions may be defined by detents in the housing. The cantilever member may support the motor, and typically also the lift transmission and the cutting transmission. Typically, the lift-generating member will be mounted about the mounting point, with the motor mounted between the lift-generating member and the cutting member. The cutting chamber may be provided with a suction source, whereby cut grass can be pulled off the cutting element. This replaces the prior art systems where the grass is thrown and blown off the blade by a air-displacing part of the cutting element; by providing a suction source, the invention can provide a reduction in the amount of cut grass that adheres to the internal walls of the cutting chamber. By sucking air from the cutting chamber, rather than blowing air therefrom, the lawnmower can also be made more resistant to blockages in the path of grass.

Typically, the lawnmower will comprise a path for cut grass leading from the cutting element towards the suction source. The lawnmower will typically comprise a grass box, which may represent an end of the path distal from the cutting element. Preferably, the path will be straight, thus avoiding grass being pulled around a corner and so being deposited on the walls of such a corner.

The suction source may comprise the lift-generating member; thus air may be drawn from the cutting chamber (typically indirectly) into the lift chamber, typically via the grass box. The grass box may have perforated walls, which will block the flow of cut grass at least partially, whilst allowing air to flow.

Whilst the housing is open on the bottom surface, the housing surrounding the cutting chamber may be provided with at least one aperture therein to allow airflow into the cutting chamber. This is useful particular when the suction source is provided, as it provides a relief for the negative pressure that would otherwise build up, and so will reduce the tendency for the cutting chamber to be sucked towards the ground. The or each aperture may be above the cutting element (that is, they may be on a far side of the cutting element from the bottom surface).

In order to prevent objects being projected from the cutting element through the or each aperture, there may be provided a wall in the cutting chamber between the or each aperture and the cutting element. The wall may physically separate the cutting element and the or each aperture, but allow airflow from the or each aperture past the cutting element; as such, the wall may define a bend in an air path between the or each aperture and the cutting element.

Typically, the wall may be of the form of part of the surface of a cylinder, typically coaxial with the cutting element. Such a wall provides a smooth and continuous collection area for cut grass within the cutting chamber, reducing the amount of cut grass which adheres to the internal walls of the cutting chamber.

The lawnmower may be provided with a handle, comprising a portion arranged so as to be grasped by a user, mounted on the housing by means of a resilient coupling which, with the bottom surface lowermost, tends to bias the housing so as to raise the cutting chamber.

Thus, by providing the resilient coupling, the tendency of the cutting chamber to tip towards the ground, either due to the suction source or merely because the lift- generating member tends to lift the lift chamber but not the cutting chamber, is at least partially ameliorated. Furthermore, the resilient coupling may tend to counterbalance the weight of the handle, thus providing a handle that feels light in a user's hand. Typically, with the bottom surface lowermost, the handle may be able to pivot about a horizontal axis about the resilient coupling relative to the housing. The resilient coupling may apply a biasing torque about the horizontal axis. Typically, the handle may only have a single degree of rotational freedom relative to the housing. The resilient coupling will preferably comprise a torsion spring, although extension or compression springs could also be used.

With the cutting chamber at a front of the housing and the lift chamber at a rear of the housing (front typically being furthest from the second portion), the resilient coupling will typically tend to tip the front of the housing upwards.

According to a second aspect of the invention, there is provided a lawnmower comprising: a housing open on a bottom surface thereof and defining a cutting chamber; a cutting element in the cutting chamber mounted for rotation about a generally vertical axis; and a cantilever member on which the cutting element is mounted; the cantilever member being fixed to the housing at a mounting point distal to the cutting element; flexure of at least one of the housing and the cantilever member allowing the cutting member to move generally along its vertical axis relative to the housing.

Thus, this provides a convenient way of allowing a height adjustment for the cutting element without the user having to re-fix the cutting element. The movement of the cutting member generally along its vertical axis will typically not be entirely linear, but will involve a component of pivotal motion about a point near to the mounting point. However, because the mounting point is distal from the cutting element, the movement will typically be approximately linear. The lawnmower may further comprise an adjuster, which drives flexure of at least one of the cantilever and the housing so as to move the cutting element. The adjuster may be manipulable by a user with the bottom surface lowermost. Thus, the user does not have to turn the lawnmower over when adjusting the cutting height. The adjuster may comprise a cranked bar having a cranked portion which works in a slot in the cantilever member, rotation of the cranked bar causing movement of the cantilever relative to the housing.

The lawnmower may further comprise a locking mechanism whereby the position of the cantilever relative to the housing can be fixed, thereby fixing the position of the cutting member relative to the housing along its vertical axis. The adjuster may comprise the locking mechanism, which may comprise a lever fixed to the cranked bar, typically which is biased against the housing. Typically, the adjuster will have a plurality of discrete positions at which the adjuster locks the position of the cutting member along its vertical axis; the discrete positions may be defined by detents in the housing.

The cantilever member may support a motor of the lawnmower.

The lawnmower may comprise a cutting transmission, having an input rotatable about a first cutting transmission axis and an output rotatable about a second cutting transmission axis, the first cutting transmission and second cutting transmission axes being spaced from one another, the input being coupled to the output so as to transmit rotation of the input to rotate the output, the input being coupled to the output shaft of the motor and the output being coupled to the cutting member, the cutting transmission also being supported by the cantilever member.

The housing may further define a lift chamber, the lawnmower comprising lift- generating means arranged to generate lift in the lift chamber. The lift-generating means may comprise a lift-generating member in the lift chamber.

The lawnmower may be in accordance with the first aspect of the invention, and may have any of the optional features described above.

According to a third aspect of the invention, there is provided a lawnmower comprising: a housing open on a bottom surface thereof and defining a cutting chamber and a lift chamber on the bottom surface; a cutting element in the cutting chamber; and a lift-generating means arranged to generate lift in the lift chamber, the housing surrounding the cutting chamber being provided with at least one aperture therein to allow airflow into the cutting chamber.

This provides a relief for any negative pressure that would otherwise build up in the cutting chamber, and so will reduce the tendency for the cutting chamber to be sucked towards the ground. This is particularly useful where the cutting chamber is provided with a suction source, whereby cut grass can be pulled off the cutting element. The or each aperture may be above the cutting element (that is, they may be on a far side of the cutting element from the bottom surface).

The lift-generating means may comprise a lift-generating member in the lift chamber. The lawnmower may be in accordance with any of the preceding aspect of the invention, and may have any of the optional features described therein. According to a fourth aspect of the invention, there is provided a lawnmower comprising: a housing open on a bottom surface thereof and defining a cutting chamber on the bottom surface; a cutting element in the cutting chamber; and a handle comprising a portion arranged so as to be grasped by a user, the handle and the housing being joined by means of a resilient coupling which, with the bottom surface lowermost, tends to bias the housing so as to raise the cutting chamber.

Thus, by providing the resilient coupling, any tendency of the cutting chamber to tip towards the ground is at least partially ameliorated. The tendency may, for example, be due to a lift chamber being provided on the bottom surface separate from the cutting chamber, or from the provision of a suction source in the cutting chamber, or merely because the lawnmower is not perfectly balanced. Furthermore, the resilient coupling may tend to counterbalance the weight of the handle, thus providing a handle that feels light in a user's hand. The handle may be able to pivot about the resilient coupling relative to the housing; typically, with the bottom surface lowermost, typically about a horizontal axis. The resilient coupling may apply a biasing torque about the horizontal axis. The resilient coupling will preferably comprise a torsion spring, although extension or compression springs could also be used.

The lift-generating means may comprise a lift-generating member in the lift chamber. The lawnmower may be in accordance with any of the preceding aspect of the invention, and may have any of the optional features described therein.

There now follows, by way of example only, embodiments of the present invention, described with reference to the accompanying drawings, in which:

Figure 1 shows a front elevation of a lawnmower in accordance with an embodiment of the invention;

Figure 2 shows a vertical cross section through the lawnmower of Figure 1 , along line A-A of Figure 1 ; Figure 3 shows a vertical cross section through the lawnmower of Figure 1 , along line B-B of Figure 1 ;

Figure 4 shows an underside plan view of the lawnmower of Figure 1 ; Figure 5 shows a perspective view of the drive train of the lawnmower of

Figure 1 , viewed from the top thereof;

Figure 6 shows a perspective view of the drive train of Figure 5, viewed from the underside thereof; Figures 7 and 8 show partial cross sectional views of the lawnmower of Figure 1 , along line A-A of Figure 1 , showing the cantilevered motor mounting plate in two extremes of adjustment; and Figure 9 shows a partial cross sectional view of the front of the lawnmower of

Figure 1 , showing the airflow through apertures in the housing.

A lawnmower in accordance with an embodiment of the invention is shown in the accompanying drawings. The lawnmower is a hover mower. The lawnmower comprises a housing 1 which is open on a bottom surface 2 thereof; in use, this surface would be positioned lowermost, so as to face the grass to be cut. The housing 1 defines two open chambers on the bottom surface 2: a cutting chamber 3 and a lift chamber 4. The housing 1 also supports a handle 5 graspable by a user. The handle 5 is connected to the housing at the rear thereof; in use, the user would walk behind the lawnmower with the handle 5 rearmost in order to propel the lawnmower.

The cutting chamber 3 is at the front of the lawnmower and contains a cutting element being a rotary blade 6. The blade 6 is rotatably mounted on a generally vertical (relative to the ground with the bottom surface 2 on the ground) axis 7. The cutting chamber is of generally circular outline (as shown in the plan view of Figure 4 of the accompanying drawings) so as to surround the blade 6 but leave some clearance. The lift chamber 4 is behind the cutting chamber 3, at the rear of the lawnmower. A lift generating member of the form of an impeller 8 is mounted for rotation about a generally vertical (relative to the ground with the bottom surface 2 on the ground) axis 9. The impeller 8 is a mixed-flow fan, which have the advantage of being particularly quiet in operation.

Indeed, the fact that the impeller 8 is mounted in the lift chamber 4 and is run at a different speed to the blade and the motor output shaft allows a wider choice of impellers to be chosen than if the impeller were directly run off the motor output and hence restricted to a particular speed of operation. Furthermore, the losses inherent in providing the impeller in a chamber remote from the lift chamber and ducting the airflow to that chamber are greatly reduced, as the impeller provides the airflow where it is needed.

As will be described below, the blade 6 and the impeller 8 are driven for rotation about their respective axes 7, 9. The cutting element 6 and the impeller 8 can be driven at different speeds in order to carry out their respective functions. The blade 6 will cut grass, whereas the impeller will force a cushion of air downwards, thus lifting the lawnmower off the grass for easy movement of the lawnmower. In order to drive the blade 6 and the impeller 8, there is provided a drive train 10 shown in more detail in Figures 5 and 6 of the accompanying drawings. The drive train 10 comprises an electric motor 1 1 mounted centrally on an elongate mounting plate 12. The motor 1 1 has an output shaft 13, energisation of the motor 1 1 causing the output shaft 13 to rotate.

The mounting plate 12 supports two pulleys 14, 15, one at each end of the mounting plate; each pulley is free to rotate relative to the mounting plate 12. Each pulley 14, 15, is connected to the output shaft 13 by means of a belt 16, 17. The belts 16, 17 and the pulleys 14, 15 thereby represent two belt transmissions, whereby rotation of the output shaft 13 is transmitted to the pulleys 14, 15. Note that the pulleys 14, 15 are of differing diameter, which means that the rotational speed at which the pulleys rotate for a given rotational speed of the output shaft 13 will be different. The belt drives transmit the rotation of the output shaft about axis 18 to the axes 19, 20 of rotation of the pulleys 14, 15; the axes 19, 20 are spaced from the axis 18.

The blade 6 will be mounted on a spindle 21 of pulley 15, whereas the impeller 8 will be mounted on a spindle 22 of pulley 14. The pulley 15 is larger than the pulley 14, which means that the impeller 8, which is coupled to the smaller pulley, will rotate faster than the blade 6. Furthermore, axis 19 will be coincident with vertical axis 7, whilst axis 20 will be coincident with vertical axis 9.

As can be seen from Figures 7 and 8 of the accompanying drawings (not shown in the other drawings), this arrangement allows the motor 1 1 to be situated in the centre of the housing 1 ; given that the motor 1 1 is one of the heaviest parts of the lawnmower, being able to position the motor 1 1 in the centre of the housing (rather than, say, over the lift chamber 4) means that a more balanced lawnmower results.

The mounting plate 12 is fixed to the housing 1 at the end carrying the pulley 14 coupled to the impeller; fixing lugs 39 will be fixed to the housing using screws. Whilst this means that the impeller end of the mounting plate is fixed relative to the housing 1 , both the housing 1 and the mounting plate 12 are flexible to some extent. This means that the mounting plate 12 is cantilevered from the housing 1 , and so the blade end is free to move in an approximately vertical manner.

This can be used to allow height adjustment of the blade 6 relative to the housing, and so the height at which the grass will be cut. A lever 23 is provided supported on the housing 1 , so as to be biased against the housing against several detents, so as to provide a plurality of fixed positions of the lever. The lever 23 comprises a shaft 38 having a cranked portion 37 which works in slot 24 in the mounting plate 12. Rotation of the lever 23 about the shaft 38 causes the cranked portion 37 to force the blade 6 end of the mounting plate 12 to be driven upwards or downwards under the action of the cranked portion of the lever 23. The height of the blade 6 can therefore easily be adjusted by a user without having to upend the lawnmower or access the (typically messy) underside or physically interact with the blade in any way.

The lawnmower further comprises a removable grass box 24. The grass box 24 has a perforated bottom side 36, which, when the grass box 24 is placed on the lawnmower, is positioned above the impeller 8. When rotated by the motor 1 1 , the impeller 8 sucks air from the grass box 24 through the perforated bottom 36 into the lift chamber 4. The grass box 24 is connected to the cutting chamber 3 via a grass chute 25. Thus, because of the negative (with respect to atmospheric) pressure in the grass box 24, air will be sucked from the cutting chamber through the grass chute 25 into the grass box, with grass entrained.

It is to be noted that the grass chute 25 provides a path for grass from the blade 6 to the grass box 24; in Figure 3 it can be seen that a straight path 26 exists in the region shown in that Figure. This means that cut grass is less likely to adhere to the side of the cutting chamber 3 or the grass chute 25, as it does not have any corners to negotiate. Furthermore, as the grass is lifted off the blade 6 by the suction from the grass box 24, there is no need for the blade to be shaped so as to throw the grass off in a particular direction or to generate any airflow; a simple straight-edged blade can be used. As shown in Figure 9 of the accompanying drawings, there are provided apertures 26 in the housing which allow the passage of air into the cutting chamber 3. This will relieve the negative (relative to atmospheric) pressure which will build up in the cutting chamber 3 due to suction of air into the grass box 24. Without such apertures 26, the negative pressure would tend to suck the housing around the cutting chamber 3 down towards the ground, tending to tip the lawnmower towards its front end and making it less manoeuvrable.

In order to prevent objects being projected from the apertures 26 by the blade a part- cylindrical wall 27 is provided, coaxial with the blade 6 but of slightly greater radius, and surrounding the blade so as to block any straight path from the blade to the apertures. Given that a part-cylindrical wall will present a smooth surface to cut grass and the like, there is likely to be little accumulation of cut grass on this surface. Air will follow the curved path 28 into the cutting chamber 3 before entraining cut grass off the blade and following path 26 into the grass box 24.

As discussed above, the handle 5 is supported off the housing 1. The handle 5 is connected at a lower end to the housing 1 so as to pivot about horizontal axis 34. An upper portion 30 of the handle 5 carries the controls 31 for the lawnmower, such as an on/off switch. The handle 5 is generally U-shaped, with the user grasping the cross- piece of the U-shape adjacent to the controls 31 , and each of the ends of the U being coupled to the housing.

The handle 5 is mounted on the housing 1 by resilient couplings 32 such as torsion springs. The resilient couplings 32 allow the handle 5 to pivot about the horizontal axis 34 relative to the housing 24, whilst tending to bias the handle 5 relative the housing 1 such that the handle 5 tends to tip the housing 1 backwards in the direction of arrow 35. The combined effect is to tend to counteract the tendency of the lawnmower to tip forwards, given that the lift chamber 4 is at the back of the housing, and to balance the weight of the handle 5 for the user. Thus, the lawnmower is more stable, and the user feels more comfortable.

Claims

1. A lawnmower comprising: a housing open on a bottom surface thereof and defining a cutting chamber and a lift chamber on the bottom surface; a cutting element in the cutting chamber; and a lift-generating member in the lift chamber, in which the cutting element and the lift-generating member are mounted for rotation about generally vertical axes which are generally perpendicular to the bottom surface.

2. The lawnmower of claim 1 , in which the lift-generating member comprises an impeller, such as a mixed-flow fan.

3. The lawnmower of claim 1 or claim 2, comprising a motor having an output shaft and a lift transmission having an input rotatable about a first lift transmission axis and an output rotatable about a second lift transmission axis, the first lift transmission and second lift transmission axes being spaced from one another, the input being coupled to the output so as to transmit rotation of the input to rotate the output, the input being coupled to the output shaft of the motor and the output being coupled to the lift-generating member.

4. The lawnmower of claim 3, comprising a cutting transmission, having an input rotatable about a first cutting transmission axis and an output rotatable about a second cutting transmission axis, the first cutting transmission and second cutting transmission axes being spaced from one another, the input being coupled to the output so as to transmit rotation of the input to rotate the output, the input being coupled to the output shaft of the motor and the output being coupled to the cutting member.

5. The lawnmower of claim 4, in which the first cutting transmission axis and the first lift transmission axis are coincident with the output shaft of the motor, the second cutting transmission axis being coincident with the vertical axis of the cutting member and the second lift transmission axis being coincident with the vertical axis of the lift- generating member.

6. The lawnmower of any of claims 3 to 5, in which the motor is provided closer to the centre of extent of the housing in a horizontal plane than to the edge of the extent of the housing.

7. The lawnmower of any of claims 3 to 6, comprising a grass box for the collection of cut grass, the motor not being surrounded by any part of the grass box.

8. The lawnmower of any preceding claim, in which the cutting element is mounted on a cantilever member, the cantilever member being fixed to the housing at a mounting point distal to the cutting element; flexure of at least one of the housing and the cantilever member allowing the cutting member to move generally along its vertical axis relative to the housing.

9. The lawnmower of claim 8, comprising an adjuster, which drives flexure of at least one of the cantilever and the housing so as to move the cutting element.

10. The lawnmower of claim 9, in which the adjuster is manipulable by a user with the bottom surface lowermost.

1 1. The lawnmower of claim 9 or claim 10, the adjuster comprises a cranked bar having a cranked portion which works in a slot in the cantilever member, rotation of the cranked bar causing movement of the cantilever relative to the housing.

12. The lawnmower of any of claims 8 to 1 1 , in which the cantilever member supports the motor,

13. The lawnmower of claim 12 as dependent from claim 4, in which the cantilever member supports the lift transmission and the cutting transmission.

14. The lawnmower of any preceding claim, in which the cutting chamber is provided with a suction source, whereby cut grass can be pulled off the cutting element.

15. The lawnmower of claim 14, comprising a path for cut grass leading from the cutting element towards the suction source and a grass box, the grass box representing an end of the path distal from the cutting element, the path being straight.

16. The lawnmower of claim 14 or claim 15, in which the suction source comprises the lift-generating member.

17. The lawnmower of claim 16 as dependent on claim 15, arranged such that air can be drawn from the cutting chamber into the lift chamber via the grass box.

18. The lawnmower of any of claims 14 to 17, in which the housing surrounding the cutting chamber is provided with at least one aperture therein to allow airflow into the cutting chamber.

19. The lawnmower of claim 18, in which the or each aperture is above the cutting element.

20. The lawnmower of claim 18 or claim 19, in which there is provided a wall in the cutting chamber between the or each aperture and the cutting element.

21. The lawnmower of claim 20, in which the wall physically separates the cutting element and the or each aperture, but allows airflow from the or each aperture past the cutting element, the wall defining a bend in an air path between the or each aperture and the cutting element.

22. The lawnmower of claim 20 or claim 21 , in which the wall is of the form of part of the surface of a cylinder, typically coaxial with the cutting element.

23. The lawnmower of any preceding claim, comprising a handle comprising a portion arranged so as to be grasped by a user, mounted on the housing by means of a resilient coupling which, with the bottom surface lowermost, tends to bias the housing so as to raise the cutting chamber.

24. The lawnmower of claim 23, in which, with the bottom surface lowermost, the handle can pivot about the resilient coupling relative to the housing about a horizontal axis, the handle having only a single degree of rotational freedom relative to the second portion.

25. The lawnmower of claim 23 or claim 24, in which, with the cutting chamber at a front of the housing and the lift chamber at a rear of the housing, the resilient coupling will tend to tip the front of the housing upwards.

26. A lawnmower comprising: a housing open on a bottom surface thereof and defining a cutting chamber; a cutting element in the cutting chamber mounted for rotation about a generally vertical axis; and a cantilever member on which the cutting element is mounted; the cantilever member being fixed to the housing at a mounting point distal to the cutting element; flexure of at least one of the housing and the cantilever member allowing the cutting member to move generally along its vertical axis relative to the housing.

27. The lawnmower of claim 26, comprising an adjuster, which drives flexure of at least one of the cantilever and the housing so as to move the cutting element.

28. The lawnmower of claim 27, in which the adjuster is manipulable by a user with the bottom surface lowermost.

29. The lawnmower of claim 27 or claim 28, in which the adjuster comprises a cranked bar having a cranked portion which works in a slot in the cantilever member, rotation of the cranked bar causing movement of the cantilever relative to the housing.

30. The lawnmower of any of claims 27 to 29, in which the adjuster comprises a locking mechanism whereby the position of the cantilever relative to the housing can be fixed, thereby fixing the position of the cutting member relative to the housing along its vertical axis.

31. The lawnmower of claim 30, in which the locking mechanism comprises a lever fixed to the cranked bar, the lever being biased against the housing, the adjuster having a plurality of discrete positions at which the adjuster locks the position of the cutting member along its vertical axis; the discrete positions being defined by detents in the housing.

32. The lawnmower of any of claims 26 to 31 , in which the cantilever member supports a motor of the lawnmower.

33. The lawnmower of claim 32, comprising a cutting transmission, having an input rotatable about a first cutting transmission axis and an output rotatable about a second cutting transmission axis, the first cutting transmission and second cutting transmission axes being spaced from one another, the input being coupled to the output so as to transmit rotation of the input to rotate the output, the input being coupled to the output shaft of the motor and the output being coupled to the cutting member, the cutting transmission also being supported by the cantilever member.

34. A lawnmower comprising: a housing open on a bottom surface thereof and defining a cutting chamber and a lift chamber on the bottom surface; a cutting element in the cutting chamber; and a lift-generating means arranged to generate lift in the lift chamber, the housing surrounding the cutting chamber being provided with at least one aperture therein to allow airflow into the cutting chamber.

35. The lawnmower of claim 34, in which the or each aperture is above the cutting element.

36. The lawnmower of claim 34 or claim 35, comprising a wall in the cutting chamber between the or each aperture and the cutting element.

37. The lawnmower of claim 36, in which the wall physically separates the cutting element and the or each aperture, but allows airflow from the or each aperture past the cutting element, the wall defining a bend in an air path between the or each aperture and the cutting element.

38. The lawnmower of claim 36 or claim 37, in which the wall is of the form of part of the surface of a cylinder.

39. A lawnmower comprising: a housing open on a bottom surface thereof and defining a cutting chamber on the bottom surface; a cutting element in the cutting chamber; and a handle comprising a portion arranged so as to be grasped by a user, the handle and the housing being joined by means of a resilient coupling which, with the bottom surface lowermost, tends to bias the housing so as to raise the cutting chamber.

40. The lawnmower of claim 39, in which the handle is able to pivot about the resilient coupling relative to the housing.

41. The lawnmower of claim 40, in which, with the bottom surface lowermost, the handle is able to pivot relative to the housing about a horizontal axis about the resilient coupling.

42. The lawnmower of claim 41 , in which the handle has only a single degree of rotational freedom relative to the housing.

43. The lawnmower of claim 41 or claim 42, in which the resilient coupling applies a biasing torque about the horizontal axis.

44. The lawnmower of any of claims 39 to 43, in which the resilient coupling comprises a torsion spring.

45. The lawnmower of any of claims 39 to 44 in which housing is provided with a lift chamber on a bottom surface thereof, the lawnmower comprising a lift-generating means arranged to generate lift in the lift chamber.

46. The lawnmower of claim 45, in which the cutting chamber is at a front of the housing and the lift chamber at a rear of the housing, the resilient coupling tending to tip the front of the housing upwards.