GB2318967A - Lawnmower - Google Patents

Abstract

A lawnmower includes a cutting blade (10), and a motor (1) having a drive shaft (2). An inner shroud (4) and an outer shroud (5) are spaced apart from each other to form a passageway (12) therebetween. The motor (1) is disposed within, and spaced apart from, the inner shroud (4). The mower is provided with an air inlet (6), and an impeller (3) for drawing air through the air inlet, and for directing at least a part of that air through the passageway (12).

Description

A LAWNMOWER This invention relates to a lawnmower, and in particular to a lawnmower having an impeller for creating a flow of air.

US Patent No. 4194345 discloses a lawnmower including an electric motor mounted on a body, the motor being surrounded laterally by an upwardly-extending annular wall formed as part of the body. A ventilator is mounted at the upper end of the motor shaft, so that rotation of the motor will direct some air between the motor and the annular wall in order to cool the motor. The lawnmower disclosed in this US Patent is limited in its effectiveness since the ventilator is not ideally placed to generate a large air flow between the motor and the annular wall. Where a significant air flow is required, the arrangement of the US Patent would be inadequate.

According to the present invention, a lawnmower comprises a cutter blade, a motor having a drive shaft, an inner shroud and an outer shroud which are spaced apart from each other to form a passageway therebetween, and with the motor disposed within, and spaced apart from, the inner shroud, an air inlet, and an impeller for drawing air through the air inlet and for directing at least a part of that air through the passageway.

Such a lawnmower operates with improved efficiency in its generation of air flow. The inner shroud reduces the resistance which would otherwise need to be overcome if the air were passed directly over the surface of the motor.

Preferably, the impeller is disposed within the outer shroud, but outside the inner shroud. This is done in order to improve the performance of the impeller.

Preferably, the air outlet is disposed in the outer shroud.

Preferably, the inner shroud includes a port through which an air stream is drawn by the impeller from the motor. This air stream cools the motor.

Preferably, the motor includes airways therethrough for the passage of the air stream for cooling.

Preferably the impeller is double-sided, including a first side for drawing air from the air intake, and a second side for drawing the air stream from the motor.

The double-sided impeller increases the efficiency of the machine.

Preferably, the lawn mower includes a hood, and the passageway directs air under the hood to support the lawnmower above the ground. The flow of air generated by the impeller is therefore used to support the mower.

Preferably, the hood includes a diffuser for distributing the air directed from the passageway beneath the hood. Not only is the diffuser able to direct the flow of air towards the sides of the hood, so as to increase the support effect of the air, but the diffuser also assists in distributing the pressurised air beneath the hood which is of particular use when heavy parts of the lawnmower are disposed towards one side of the mower.

The invention will now be described by way of example only with reference to the drawing, the single figure of which shows a lawnmower in section.

Referring to the drawing, a lawnmower includes a motor 1 mounted on a hood 9. The hood 9 forms a cutting chamber in which a cutter blade 10 rotates during use. In use, the lawnmower is supported by pressurised air directed beneath the hood 9.

The motor 1 drives a drive shaft 2 which passes through the entire length of the motor 1. The cutter blade 10 is mounted at the lower end of the drive shaft 2, the cutter blade being rotatable about a vertical axis within the hood 9. An impeller 3 is mounted at the upper end of the drive shaft 2. An inner shroud 4 is disposed around the motor 1 thereby enclosing it. The impeller 3 lies outside the inner shroud 4. An outer shroud 5 is disposed around the motor 1 and the impeller 3. The outer shroud 5 is disposed outside the inner shroud 4, leaving an annular passageway 12 therebetween. The lower end of the passageway 12 opens beneath the hood 9. The outer shroud 5 includes an air intake 6 located adjacent to the centre of the impeller 3 whereby, in use, while the impeller rotates, air is drawn through the air intake into the passageway 12 between the inner and outer shrouds 4 and 5. The inner shroud 4 includes a port 7 opening into the passageway 12. While the impeller 3 rotates, an air stream is drawn into the passageway 12 from within the motor 1, and this air stream is used to cool the motor 1.

The motor 1 also includes an air inlet 8 which leads ambient air to cool the motor.

The hood 9 includes a diffuser 11 which directs the flow of air from the passageway 12 under the hood so as to create generally a level hover.

The impeller 3 is double sided. The first side of the impeller 3 draws air through the air intake 6, whereas the second side draws air from the motor 1 via the port 7.

Both sides of the impeller 3 exhaust air into the passageway 12 between the inner and outer shrouds 4 and 5.

When the motor 1 is switched on, the drive shaft 2 is driven. The drive shaft 2 powers the impeller 3 and the cutter blade 10 so that they rotate about a vertical axis.

The first side of the impeller 3 draws air through the air intake 6 into the passageway 12, and the second side of the impeller 3 draws air from within the motor 1 into the passageway 12. The air stream passing through the motor 1 cools the motor, whereas the air entering the machine via air intake 6 would typically be taken from the atmosphere. Air from the impeller 3 is blown through the passageway 12, and under the hood 9. The diffuser 11 then directs the flow of air within the hood 9 so as to optimise the hover effect by which the hood is supported above the ground by the flow of air. The cutter blade 10 is then able to cut the grass, and a user of the lawnmower is able to manoeuvre the lawn mower easily across a lawn to be cut.

According to another embodiment, not shown, the air sucked into the machine via the air intake 6 is used to suck cut grass into a grass box. The grass box is typically supported above the hood and around the motor.

The grass box would normally collect grass directly from the ground behind the mower. In normal use, as the lawnmower is pushed forwards, cut grass is left in a windrow behind the mower. The inlet to the grass box may be located behind the mower, and positioned so as to collect the windrow. The grass box includes a filter which is used to remove the cut grass from the air stream before it enters the air intake 6.

According to another embodiment, the impeller is replaced by two separate impellers, one of which draws air from the air intake, and the other of which draws air from the port. These impellers may be of different sizes, or arranged to rotate at different angular velocities.

Claims (8)

1. A lawnmower comprising: a cutter blade; a motor having a drive shaft; an inner shroud and an outer shroud which are spaced apart from each other to form a passageway therebetween, and with the motor disposed within, and spaced apart from, the inner shroud, an air inlet; and an impeller for drawing air through the air inlet, and for directing at least a part of that air through the passageway.

2. A lawnmower according to claim 1, wherein the impeller is disposed within the outer shroud, but outside the inner shroud.

3. A lawnmower according to claim 1 or claim 2, wherein the air inlet is disposed in the outer shroud.

4. A lawnmower according to any preceding claim. wherein the inner shroud includes a port through which an airstream is drawn by the impeller from the motor.

5. A lawnmower according to claim 4, wherein the motor includes airways therethrough for the passage of the airstream for cooling.

6. A lawnmower according to claim 4 or claim 5, wherein the impeller is double-sided, including a first side for drawing air from the air intake, and a second side for drawing the air stream from the motor.

7. A lawnmower according to any preceding claim, including a hood, beneath which air is directed by the passageway to support the lawnmower above the ground.

8. A lawnmower according to claim 7, wherein the hood includes a diffuser for distributing the flow of air directed from the passageway beneath the hood.