GB2254991A - Rotary mowers with grass collection. - Google Patents

Abstract

A ground-supported rotary lawnmower has a cutter (2) rotatable about a generally vertical axis beneath a protective shroud or deck (9). A grass collection system for the mower includes a fan (5) arranged to suck air from a grass collection chamber (15) and exhaust air to the atmosphere, the chamber (15) having a suction nozzle (7) arranged to pick-up grass cuttings from the ground, and means (16) for separating the grass cuttings from the air flow through the chamber. <IMAGE>

Description

ROTARY MOWeRS WITH GRASS COLLECTION This invention relates to ground-supported rotary lawnmowers, that is to say ground-supported lawnmowers in which the cutter element is rotatable about a generally vertical axis.

Previous attempts to provide low cost ground-supported rotary mowers with grass collection have been disappointing because they often suffer from stalling and poor cutting due to insufficient power. This lack of power also results in poor grass collection on anything other than dry straw-like grass7 due to collection chutes becoming clogged.

The market requirement for rotary mowers to have a rear roller to assist in cutting up to edges, and to give a striped effect to the lawn, has increased the difficulty of providing a satisfactory collection system because of the need to lift the cut grass in the air stream over the rear roller to reach the collection box. This further increases power consumption and hence cost.

Pending legislation will require metal bladed mowers to comply with maximum stopping time" limits which can normally be achieved only by the addition of a blade brake at additional cost. The alternative is to use pivoting plastic cutting sticks which are intrinsically safe.

These are effective at grass cutting but totally ineffective at providing the air flow to assist grass collection that is often achieved by turning up the trailing edge of a rotary metal blade.

According to the present invention, there is provided a grass collection system for a ground-supported rotary lawnmower wherein a forced air circulation device sucks air from a grass collection chamber and exhausts air to the atmosphere. The chamber preferably has a suction pick-up nozzle through which grass cuttings lying on the ground are sucked when the circulation device is energised, and some means for separating the grass cuttings from the air flow through the chamber.

In one embodiment of the invention, a small proportion of the exhaust air is exhausted beneath a shroud or deck protecting the cutter.

The cutter is preferably driven by a motor, and the forced air circulation device preferably comprises a fan driven by the same motor, although the fan may or may not rotate about the same axis as the cutter.

In the accompanying drawings, by way of example only: Figure. 1 is a diagrammatic illustration of a grass collection system for a rotary lawnmower according to a first embodiment of the invention; and Figure. 2 is a diagrammatic illustration of a grass collection system for a rotary lawnmower according to a second embodiment of the invention.

Referring to Fig. 1, a powered rotary lawnmower has a motor 1 driving a cutting element 2 about a vertical axis, the cutting element being in the form of a plastic cutting stick pivotally mounted on a pin 3 projecting downwardly from the underneath surface of a disc 4. The pin 3 is located toward the outer periphery of the disc 4.

The mower is supported on front and rear roller/wheels 8a, 8b, and the cutter assembly rotates beneath a shroud or deck 9 having a central opening 10 for the motor shaft 11. The motor 1 is enclosed in a protective housing 12 supported over the deck 9, and also drives a centrifugal fan 5 which is carried on the shaft 11 above the deck 9.

The fan 5 is positioned in a chamber 22 formed between the top surface of the deck 9 and the underneath surface of the motor housing 12.

When the motor is energised to drive the cutter/fan assembly, air is sucked into the fan chamber 22 through an opening 20 in the base of the motor housing and is exhausted directly to the atmosphere through an opening 23 in the front wall 24 of the chamber 22.

The motor housing 12 has two separate air inlets 13, 14 located respectively in a top wall 241 and a rear wall 25 of the housing. The inlet 14 in the rear wall is aligned with an opening 27 in a front wall 26 of a grass collection chamber 15 attached to the rear of the mower.

When the motor is energised, air drawn by the fan 5 through the top inlet 13 cools the motor7 while air drawn through the rear inlet 14 is sucked from the grass collecting chamber 15 which includes at least one suction pick-up nozzle 17 located in the bottom wall 28 of the chamber and extending downwardly toward the ground behind the rear roller/wheels 8b. Alternatively, the chamber 15 could be extended forwards with the nozzle 17 positioned immediately in front of rather than behind the rear roller/wheels 8b. The collecting chamber 15 also includes means for separating grass cuttings from the air stream, and this means may take the form of a slotted or perforated plate 16 partitioning the chamber.

The collection chamber 15 is releasably attached to the rear of the motor housing 12 in any convenient manner. For maximum efficiency an air-tight seal is formed around the aligned openings 14 and 27. For example, a labyrinth seal might be used.

In operation, rotation of the fan 5 produces a flow of air shown by the arrows in the figure, and the grass cut by the cutting stick 2 is sucked up through the nozzle 17 into the collecting chamber 15. The natural windrowing effect of the rotary mower ensures that the cut grass is in a line or stripe lying on the ground before the suction nozzle 17 reaches it.

Accordingly, an efficient grass collection system is provided while at the same time permitting the use of plastic cutting sticks and, optionally, a relatively low-cost plastic deck of, say, polyethylene or polypropylene. The use of plastic cutting sticks avoids the need for blade braking, thus further reducing costs. The motor cannot be stalled as the cutting system cannot be jammed, and there is no need to protect the motor against high overload or stall conditions. A further advantage of the suction pick- up is that it is less likely to cause clogging with wet/damp/lush grass than a positive pressure collection system or a system where the cut grass is wholly or in part impelled by the cutter blade toward the grass collector.

By removing the cutting stick 2 of the mower, the mower is converted to a suction cleaner for collecting garden debris.

The suction pick-up nozzle 17 of the collection chamber 15 may lie within or outside the mower deck 9, and may be extended through a flexible hose (not shown) to provide access into restricted areas. The nozzle may have a variable aperture to suit different grass conditions and/or size and type of debris to be collected.

Since the mower is supported on rollers and/or wheels, it is not necessary to pressurise the area beneath the deck as in a so-called hovermower, so that the air exhausted from the fan can be directed as required to reduce noise and/or disturbance to both the cut grass awaiting collection and the uncut grass approaching the cutting element. Moreover, since the suction fan is venting to atmosphere, it will 1 draw less power for equivalent suction performance, or alternatively give superior suction performance for the same power, compared to a system in which the fan outlets to positive pressure under the mower deck.

In the embodiment of Fig. 2, the same reference numerals used in Fig.

1 are used to denote like parts.

The embodiment of Fig. 2 is similar to that of Fig. 1 except that the fan 5 is positioned within a central opening 21 in the deck 9. In this case a small proportion of the air exhausted from the fan is exhausted under the deck (arrow A ) while the main discharge (arrow B) continues to exhaust directly to the atmosphere above the deck. This arrangement prevents any possibility of a low pressure zone being created in the fan chamber 22 which might otherwise suck grass cuttings into the fan chamber and block the fan outlet. The proportion of air in the 'A' stream is preferably in the range 0-20% and should not exceed 30%.

Claims (12)

1. A ground-supported rotary lawnmower comprising a cutter rotatable about a generally vertical axis beneath a protective shroud or deck; and a grass collection system including a forced air circulation device arranged to suck air from a grass collection chamber and exhaust air directly to the atmosphere.

2. A lawnmower according to claim 1 wherein at least a portion of the forced air circulation device is disposed in a chamber formed above the shroud or deck.

3. A lawnmower according to claim 2 wherein air is exhausted to the atmosphere through an opening in a wall of the chamber.

4. A lawnmower according to claim 2 or claim 3 wherein the cutter and the fan are driven by a motor enclosed within a housing and the chamber is formed between the underneath surface of the motor housing and the top surface of the shroud or deck.

5. A lawnmower according to claim 4 wherein air is sucked from the grass collection chamber through the motor housing.

6. A lawnmower according to any one of the claims 1-5 wherein the grass collection chamber includes a suction nozzle arranged to pick-up grass cuttings lying on the ground.

7. A lawnmower according to claim 3 in which the grass collection chamber includes means for separating the grass cuttings from the air flow through the chamber.

8. A lawnmower according to any one of the preceding claims wherein the forced air circulation device comprises a fan rotatable about the same axis as the cutter.

9. A lawnmower according to any one of the preceding claims wherein a small proportion of the air exhausted from the forced air circulation device is exhausted beneath the shroud or deck.

10. A lawnmower according to claim 9 wherein the forced air circulation device is disposed within an opening formed in the deck or shroud.

11. A lawnmower according to any one of the preceding claims wherein the cutter is detachable whereby, with the cutter detached, the mower is converted to a suction cleaner for collecting garden debris.

12. A lawnmower substantially as herein described with reference to Fig. 1 or Fig. 2 of the accompanying drawings.