GB2352956A

GB2352956A - Lawnmower with adjustable height of cut

Info

Publication number: GB2352956A
Application number: GB9918853A
Authority: GB
Inventors: Adrian Coussins
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1999-08-10
Filing date: 1999-08-10
Publication date: 2001-02-14
Anticipated expiration: 2019-08-10
Also published as: GB9918853D0; GB2352956B

Abstract

A lawnmower comprising a chassis having a pair of rear wheels 12a,12b and a smaller diameter rear roller 17 disposed between the rear wheels 12a,12b, the chassis and a rear axle 13 joining the rear wheels 12a,12b being moveable relative to one another to adjust the height-of-cut. A carrier assembly for the rear roller 17 is pivotably mounted on the chassis, the carrier assembly including means engaging the rear axle 13 such that the movement of the rear axle 13 relative to the chassis when adjusting the height-of cut produces a corresponding pivotable movement of the carrier assembly. Rear axle 13 locates in selected recesses 4a-b to adjust the height of cut and is biassed in place by a spring 16.

Description

2352956 ROTARY LAWNMOWERS This invention relates to a roller/wheel

assembly at the rear of a domestic rotary lawrimower.

The housing of a rotary lawnmower is generally supported on front and rear wheels, and it is known to provide the rear wheel assembly with a smaller diameter roller between the two rear wheels. The roller rotates independently about its own spindle and flattens the freshly cut grass to provide a desirable striped appearance to the cut lawn.

It is also known to raise and lower the rear wheels relative to the housing to adjust the height-of-cut of the mower. However, a problem then arises as to how to adjust the roller to accommodate the different height settings. In practice, the roller is often set so that it contacts the ground when the cutter is at its lowest height-of- cut, i.e. when the grass is at its shortest, but is lifted clear of the ground when the height-of-cut is set higher. This is obviously undesirable.

In our copending application 9817485.7 we describe an arrangement in which the roller is rotatably mounted 'in a carrier assembly and the carrier assembly is pivotally mounted on the chassis of the lawninower for movement toward and away from the ground in response to movement of rear wheel stub axles relative to the chassis when adjusting the height-of-cut. In this manner the roller is made to follow the movement of the rear wheels when adjusting the height-of-cut.

In the mechanism described in 9817485,7, the rear wheel stub axles are each carried by respective pivot arms which pivot about a rear axle fixed to the chassis. A cam surface of each pivot arm then engages a corresponding cam surface of the carrier assembly to transmit the necessary motion to the carrier assembly when the pivot arm is pivoted about the fixed rear wheel axle.

According to the present invention there is provided a rear wheel/roller assembly for a law-nmower wherein a pair of rear wheels are' oined by a rear axle and wherein a rear roller cam'er assembly is pivotally mounted on a chassis for movement toward and away from the ground, the rear axle passing through the carrier assembly such that movement of the rear axle relative to the chassis when adjusting the height-of-cut produces a corresponding pivotal movement of the carrier assembly.

The carrier assembly preferably includes an elongate slot to accommodate forward and backward movement of the rear wheel axle relative to the chassis when adjusting the height-of-cut. The elongate slot may be aligned with a corresponding slot in the chassis having a plurality of vertically spaced recesses for accommodating the rear axle. The height-of-cut is then adjusted by moving the rear axle against a resilient bias out of one recess and into another, the vertical movement of the axle being transmitted to the carrier assembly and the horizontal movement being accommodated by the elongate slot.

A rear roller/wheel assembly embodying the invention wfll now be described, by way of example only, with reference to the accompanying drawings wherein Fig. I is a perspective view of the rear portion of a rotary lawninower, the mower being tipped back-wards to reveal the underside of the deck and the rear wheel/roller assembly, and Fig. 2 is a diagrammatic sketch illustrating the operation of the height-of-cut 25 adjustment mechanism.

Referring to these drawings, the illustrated rotary lawninower has a cutter blade 10 rotatable in use about a vertical axis and disposed beneath a protective deck 11.

Two rear wheels 12a, 12b rotate about a rear axle 13. The axle passes through respective slots 14 in each side of the mower housing 15, each slot having four 3 vertically spaced recesses 14a, 14b, 14c, 14d defining different height- of-cut settings.

A spring 16 hooks around the rear wheel axle 13) to urge the axle into a selected one of the recesses 14a, 14b, 14c, 14d. As shown in Fig. 2, the axle is in the lowest recess 14d giving a maximum height-of-cut i.e. the grass is at its longest. When adjusting the height-of-cut, the axle 13 is moved rearwardly against the bias of spring 16 out of one recess and then forwardly into another recess of the slots 14.

A smaller diameter rear roller 17 is disposed between the two wheels 12a, 12b, the roller being rotatably mounted on a spindle 18. The opposite ends of the spindle 18 are rotatably mounted M' respective carrier brackets 19a, l9b which are each pivotally mounted about a back pivot 20 fixed to the respective side of the mower housing 15.

Each bracket 19 'includes an elongate slot 21 which receives the rear wheel axle 1 -3).

Accordingly, as the rear wheel axle is raised or lowered in the slots 14 to adjust the height-of-cut, there is a corresponding pivotal movement of the brackets 19a, l9b about the respective pivots 20 which raises or lowers the rear roller 17 by a proportionate amount. At the same time, the slot 21 accommodates rearward movement of the axle 13 against the bias of spring 16 when moving the axle out of one recess of the slots 14 and into another.

An effective system for automatically adjusting the height of the roller according to the selected height-of-cut is therefore achieved using only a small number of components.

9918853.4

Claims

CLAIMS:

1. A lawnmower comprising a chassis having a pair of rear wheels and a smaller diameter rear roller disposed between the rear wheels, the chassis and a rear axle joining the rear wheels being movable relative to one another to adjust the height-of cut; and wherein a carrier assembly for the rear roller is pivotally mounted on the chassis, the carrier assembly including means engaging the rear axle such that the movement of the rear ayJe relative to the chassis when adjusting the height-of-cut produces a corresponding pivotal movement of the carrier assembly.

2. A lawninower according to claim I wherein the engaging means comprises an elongate slot for receiving the rear axle.

3. A lawnrnower according to claim 2 wherein the height-of-cut is adjusted by locating the rear axle in a selected one of a plurality of vertically spaced recesses in a side opening of the chassis; the elongate slot accommodating horizontal movement of the rear axle when adjusting the height-of cut.

4. A lawninower according to claim 3 wherein the axle is retained in the selected recess by a resilient bias.

A lawnmower according to any one of the preceding claims wherein the carrier assembly comprises a pair of brackets pivotally mounted on the chassis and rotatably supporting respective opposite ends of the rear roller.

6. A lawnmower according to claim I and substantially as herein described with reference to the accompanying drawings.