GB2246939A

GB2246939A - Vegetation cutting devices

Info

Publication number: GB2246939A
Application number: GB9117654A
Authority: GB
Inventors: Andrew Sewell; Howard Bowron
Original assignee: QUALCAST GARDEN PROD
Current assignee: QUALCAST GARDEN PROD
Priority date: 1990-08-17
Filing date: 1991-08-15
Publication date: 1992-02-19
Anticipated expiration: 2011-08-15
Also published as: GB2246939B; GB9018063D0; GB9117654D0

Abstract

A vegetation cutting device, such as a lawnmower, has a fan for boosting the delivery of the cuttings to a collection chamber. Adjustable control means (17) are provided for varying the flow of air from the fan, the control means preferably varying the size of an inlet orifice (18) through which aid is sucked into the fan. Preferably the control is mounted for rotary movement and biased by a spring towards the open position. Preferably a cam and follower move the control member. <IMAGE>

Description

VEGETATION CUTTING DEVICES In a rotary vegetation cutting device, the cuttings are either allowed to fall to the ground or they are collected.

Various arrangements have been proposed for collecting the cuttings, at least some of which rely upon creating a flow of air, additional to that normally provided by rotation of the cutter1 to help carry the cuttings to a collection chamber.

In one such arrangement for a rotary lawnmower, a flow of air is created by a fan rotating about the same vertical axis as the cutter. The fan generates a vortex of air which assists in carrying the grass cuttings through an exit port into a collection bag. The bag is constructed of a mesh which allows passage of air but not grass cuttings.

The fan draws in air from a vent, and the resulting airflow from the fan, combined with the airflow produced by the lift on the back of the cutter blade, produces a strong outflow of air and grass cuttings into the collection bag.

A problem with this arrangement is that the fan is essentially acting as a blower so that in dry, dusty conditions, a substantial amount of dust is blown out with the air through the mesh of the collection bag, and from under the deck.

According to the present invention there is provided a vegetation cutting device wherein a flow of air is created by a fan to assist in carrying the cuttings to a collection chamber, and wherein adjustable control means are provided for varying the flow of air from the fan. In this manner, the flow of air can be varied according to the prevailing cutting conditions. Where the device includes a rotating cutter blade, the flow of air from the fan may boost the flow of air created by the rotating blade.

In a preferred arrangement, an axial flow of air into the fan passes through an inlet orifice, and the control means varies the size of the orifice. With the orifice closed, a small quantity of air is still sucked into the fan but with a less efficient air collection system.

In particular, in a rotary lawnmower embodying the invention, closing the inlet orifice has the effect of drawing in more air from around the sides of a deck shrouding the rotating cutter blade and fan to create an enhanced vacuuming" effect which draws additional cuttings into the flow of air and cuttings being delivered by the fan and blade into the collection chamber. Accordingly, in dry, dusty conditions, when the cuttings are lighter and less air is required to carry the cuttings into a collection bag or box, the inlet orifice is closed or the size of the inlet orifice is at least reduced, and less dust and debris is exhausted from the bag or box.

In the accompanying drawings, by way of example only: Fig. 1 is a perspective sketch of a rotary lawnmower body embodying the invention; Fig. 2 is a schematic diagram illustrating the grass collection system of the mower with the adjustable control member in an open position; Fig. 3 is a schematic diagram similar to that of Fig. 2 showing the adjustable control member in its closed position; and Fig. 4 is an exploded perspective view showing the adjustable control member and associated parts of the lawnmower.

Referring to these drawings, the illustrated rotary lawnmower has a motor (not shown) driving a cutter blade 10 about a substantially vertical axis. The motor is located below a cover 11 secured to the mower body 22 which supports the motor and shrouds the cutter blade 10. The mower runs on wheels or rollers 23.

The motor also drives a radial turbo fan 13 disposed above the cutter blade 10 and rotatable about the same axis. The fan consists of a flat disc with upstanding blades which spiral outwardly from the centre of the disc to the periphery. Rotation of the fan 13 draws in air through an annular duct 19 and discharges air radially to produce a vortex of air within a volute 12 formed in the underside of the body 22, the volute having an exit port 14 through which air and grass cuttings are discharged into a collection bag 15. The bag 15 is constructed of an exhaust mesh. One possible alternative would be a grassbox fitted with a mesh grill. A hinged flap 16 is spring biased over the port 14, the flap 16 being lifted clear of the port when the mesh bag 15 is fitted.Fig. 1 shows the mower without a collection bag, while Figs. 2 and 3 illustrate operation of the mower with a collection bag.

A small quantity of air is drawn into the fan 13 through the front grill 24 to assist cooling of the motor.

However, the flow of air into the fan 13 is mainly dependent on the position of an adjustable control member 17 which controls the flow of air through an inlet orifice 18 at the entrance of the annular duct 19 communicating with the top of the fan. The control member 17 is a circular dome-shaped moulding 31 (Fig. 4) which is normally retained in a depressed "open" position (Figs. 1 and 2) by a spring 28 but which can be twisted on a cam 30 (Fig. 4) against the bias of the spring to raise it into a "closed" position shown in Fig. 3.

The control member 17 has three angularly spaced cam follower fins 32 which engage corresponding portions of the cam track 30 when a central spindle 33 of the control member is inserted in a bore 34 of a central boss 35 bounded by the cam track. The boss 35 is disposed beneath the orifice 18 to form the annular duct 19. A screw 36 is screwed into the bottom end of spindle 33 and, with a washer 37, holds the spring in a compressed state against the underside of the boss 35. The control member 17 is thus biased downwardly toward its depressed "open" position but can be manually rotated upwardly against the bias of the spring as the cam follower fins 32 move up the inclined paths of the respective cam tracks 30.At the top end of each cam track 30 is a shallow depression which holds the control member 17 in its "closed" position and prevents the spring 28 pulling it back to its "open" position when the member is released. To return to the "open" position, the member 17 is manually rotated out of its "closed" position.

With the member 17 in its 'closed" position, the orifice 18 is blocked and the fan 13 and the cutter blade 10 are forced to draw air in from around the edge of the skirt 20 bounding the mower body 22. This creates an enhanced "vacuuming" effect that draws additional cuttings into the vortex, but is overall a less efficient air collection system so that less air is available for delivery into the collection bag 15. The reduced airflow into the bag 15 has the advantage of reducing the debris and dust exhausting from the collection bag 15 so that this "closed" position of the control member 17 is particularly useful in dry, dusty conditions.

In one alternative embodiment (not illustrated), the flow of air from the fan is controlled by an adjustable throttling device located in the fan exhaust rather than on the suction side of the fan.

Claims

1. A vegetation cutting device wherein a flow of air is created by a fan for boosting the delivery of the cuttings to a collection chamber1 and wherein adjustable control means are provided for varying the flow of air from the fan.

2. A device according to claim 1 wherein the control means varies the size of an inlet orifice through which air is sucked into the fan.

3. A device according to claim 2 in which the control means is adjustable between an open position and a closed position relative to the inlet orifice.

4. A device according to claim 3 in which the control means includes a cam follower engaging a cam whereby rotation of the control means moves the control means axially relative to the inlet orifice between its open and closed positions.

5. A device according to claim 3 or claim 4 in which the control means is resiliently biased into one of the said positions.

6. A device according to claim 5 in which the control means includes a circular dome-shaped control member resiliently biased into a depressed open position.

7. A device according to any one of the claims 2-6 in which the fan draws in air through an axial duct and discharges air radially, and in which the inlet orifice is disposed in the axial duct.

8. A device according to any one of the preceding claims in which the device comprises a rotary lawnmower having a cutter element rotatable about a substantially vertical axis, the fan being mounted above the blade for rotation about the same vertical axis.

9. A rotary lawnmower according to claim 8 wherein the control means is rotatable about the said vertical axis.