GB2242813A - Cylinder lawnmowers - Google Patents

Abstract

A grass delivery arrangement for a cylinder lawn mower has a forced air flow, preferably produced by a fan, directed along a path merging with the path of the grass cuttings impelled by the rotating cylinder. <IMAGE>

Description

CYLINDER LAWNMOWERS A cylinder or reel lawnmower for cutting grass and other vegetation generally includes a rotating spiral-bladed cutting cylinder co-operating with a static bottom blade, the interface between the cylinder and the bottom blade being sufficiently close to perform a shear cutting action.

The mower may also include a grass collection system in which the rotating action of the cylinder impels the grass cuttings into a grass box positioned either behind or in front of the cutting cylinder. The trajectory of the grass leaving the cylinder is generally a function of the cylinder diameter, the size and position of the bottom blade, and the cylinder blade rake angle, but is also affected by any shielding provided for the bottom blade and the cutting cylinder. The velocity of the thrown grass is further affected by the rotational speed of the cylinder.

A disadvantage of conventional grass collection arrangements is that the grass tends to settle gently into a pile in the grass box as it rapidly loses velocity against the natural air resistance. The lightly packed or low density grass necessitates frequent emptying or redistribution of the grass in the grass box.

A further disadvantage, particularly associated with cylinders having blades with a single helix form, is that the grass is thrown to one side of the grass box.

According to the present invention a grass delivery arrangement for a cylinder lawn mower further comprises a forced air flow directed along a path merging with the path of the grass cuttings impelled by the rotating cylinder.

The forced air flow can be used to increase the velocity and/or help control the direction of the grass cuttings being delivered to the grass collection chamber.

The forced air flow is preferably provided by the output of a fan driven by the same motor that drives the cutting cylinder.

In one embodiment, the air from the fan is distributed across the width of the cylinder with a pressure gradient such that the velocity of the air flow progressively decreases from one side of the cylinder to the other. This helps to counteract the side throw of a single helix cylinder, and produce a more uniform distribution of grass within the grassbox. In addition, the forced air flow may be selectively diverted to produce a progressive change in the direction of the air flow across the width of the cylinder.

Some embodiments of the invention are illustrated, by way of example only, in the accompanying drawings, in which: Fig. 1 is a diagrammatic sketch i 1 illustrating a grass collection arrangement for a cylinder lawnmower and showing the mower from one side, Fig. 2 is a plan view of the embodiment shown in Fig. 1, Fig. 3 is a diagrammatic sketch of one alternative embodiment, Fig. 4 is a diagrammatic sketch of a second alternative embodiment, and Fig. 5 is a diagrammatic sketch of a third alternative embodiment.

In Fig. 1, a cylinder lawnmower has a conventional single helix cutting cylinder 10 co-operating with a fixed bottom blade 11 to perform a shear cutting action. The cutting cylinder is driven by an electric motor 12 positioned at the front of the mower. The motor 12 has an output shaft carrying a drive pulley 13, and drive is transmitted by a belt or chain 25 to a driven pulley 14 secured to the drive shaft of the cutting cylinder 10.

The cylinder 10, bottom blade 11, and motor 12 are mounted in a body or framework including opposed side plates 15, 16. The remaining components of the mower framework have been omitted for clarity.

The mower is supported on wheels 17 and carries a rear grassbox 18. The grassbox can be detached from the body of the mower. The normal trajectory of the cut grass is shown by the dashed line 19 in Fig. 1. The grass is directed upwardly and rearwardly toward an overhead deflector plate 20. The plate 20 re-directs the grass cuttings along a path which is substantially parallel to the plate 20. The momentum of the grass cuttings along this path is however increased by a separate air flow from the output of a fan 21 also driven by the motor 12. The flow of air from the fan 21 is directed through a duct 22 formed in the overhead shielding plate 27, and emerges beneath the deflector plate 20 flowing in a direction substantially parallel to the deflector plate.The increased momentum of the grass cuttings can be used to produce a more tightly packed, higher density pile of grass in the grassbox, or to carry the grass cuttings a greater distance and therefor fill a larger box.

As shown in Fig. 2, the duct 22 may be formed as a volute 23, which produces a pressure gradient across the width of the exit orifice 26. In addition a row of baffle plates 24 is positioned across the exit orifice 26, the baffle plates being progressively inclined to the air flow to produce a change in the direction of the air flow which is greatest at the top (as viewed in Fig. 2) and least at the bottom.

The combined effect of the pressure gradient and the baffle plates is to produce a graded air flow that is directed across the grassbox to counteract the sidewards throw of the single helix cylinder.

In the alternative embodiments of Fig. 3, 4 and 5 the same references used in Figs. 1 and 2 are used to denote like parts. The embodiment of Fig. 3 differs from Figs. 1 and 2 in that the air flow from the fan is directed through the cutting cylinder to change the trajectory of the grass cuttings from that shown in Fig. 1 to that shown by the dashed line 19a in Fig. 3. This is achieved by positioning the exit orifice of the fan immediately in front of the cylinder, the inlet to the fan being located directly above the ground in front of the cutting cylinder such that it provides a straightening influence on the grass, causing the grass to stand upright, prior to being cut by the cutting cylinder.

In the embodiment of Fig. 4, the air flow from the fan 21 is split so that a proportion of the air flows through the cylinder 10, as in the Fig. 3 embodiment, and the remainder flows through the duct 22 above the cylinder, as in the Fig. 1 embodiment. An additional deflector 271 extending rearwardly and upwardly from the bottom blade 11 may be included to assist entrainment of the grass into the air flow generated by the fan 21.

In the embodiment of Fig. 5, the grassbox 18 is positioned in front of the mower, and the grass cuttings are impelled in a forward direction by the combined effect of the rotating cylinder 10 and a shield plate 28 curved around the rear portion of the cylinder 10 and spaced therefrom.

In other respects, the arrangement is similar to that of Fig. 1, with the duct 22 being formed between the curved shield plate 28 and the overhead shield plate 27. The air from the fan 21 thus boosts the flow of grass cuttings at the point where the cuttings are first impelled in a forward direction.

Claims (12)

1. A cylinder lawnmower comprising a rotating spiralbladed cutting cylinder co-operating with a static bottom blade to perform a shear cutting action, and means providing a forced air flow along a path merging with the path of the grass cuttings impelled by the rotating cylinder for delivering the grass cuttings into a grass collection chamber.

2. A cylinder lawnmower according to claim 1 wherein the forced air flow comprises air blown from a fan.

3. A cylinder lawnmower according to claim 2 wherein the fan and the cutting cylinder are driven by a common motor.

4. A cylinder lawnmower according to any one of the preceding claims wherein at least part of the forced air flow is directed through the cutting cylinder prior to merging with the path of the grass cuttings.

5. A cylinder lawnmower according to claim 2 wherein a suction inlet of the fan is located 7n front of the cutting cylinder relative to the direction of mowing whereby unmown grass is lifted and straightened prior to being cut.

6. A cylinder lawnmower according to any one of the preceding claims wherein the forced air flow is distributed across the width of the cutting cylinder with a velocity profile.

7. A cylinder lawnmower according to claim 6 wherein the pressure gradient counteracts the sideward throw imparted to the grass cuttings by the rotating cylinder.

8. A cylinder lawnmower according to any one of the preceding claims wherein the forced air flow is selectively diverted to produce a progressive change in the direction of the air flow across the width of the cutting cylinder.

9. A cylinder lawnmower according to claim 8 wherein the cutting cylinder is a single helix cylinder and the said change in direction is graded to counteract the sideways throw imparted to the grass cuttings by the rotating cylinder.

10. A cylindrical lawnmower according to claim 2 in which the forced air flow is distributed across the width of the mower before emerging through an exit orifice.

11. A cylinder lawnmower according to any one of the preceding claims in which at least a portion of the forced air flow is directed through an overhead duct relative to the cutting cylinder and merges with the air flow created by the rotating cylinder either immediately above or downstream of the cylinder.

12. A cylinder lawnmower substantially as herein described with reference to any one of the accompanying drawings.