GB2371202A

GB2371202A - Lawnmower height of cut adjustment

Info

Publication number: GB2371202A
Application number: GB0209238A
Authority: GB
Inventors: Adrian Coussins
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1997-08-12
Filing date: 1998-08-11
Publication date: 2002-07-24
Anticipated expiration: 2018-08-11
Also published as: GB2371202B; GB0209238D0

Abstract

The present invention relates to improvements in or relating to vegetation cutters, in particular to lawnmowers. There is described a roller assembly associated with the rear wheels 20 and a height of cut mechanism of a lawnmower; wherein the roller is mounted at each end upon a roller carrier mounted on the chassis of the lawnmower for pivotal movement thereabout; wherein the roller carrier includes a generally hook-shaped feature 61 adapted to engage a corresponding cam surface formed on the pivot arm 22. There is also described a lawnmower comprising such a roller assembly and including a height of cut adjustment mechanism, in which the height of the grass cutter above the ground is adjustable between a low cut position in which a maximum length of grass is removed by the cutter and a high cut position in which a minimum length of grass is removed; wherein the lawnmower has: a pair of front wheels or rollers mounted by means of respective stub axles on respective pivot arms carried on a front axle; and a pair of rear wheels similarly mounted on respective stub axles on pivot arms carried on a rear axle; the axles being mounted on the underside of the chassis and defining points about which the pivot arms pivot;

Description

Improvements in or relating to vegetation cutters. The present invention relates to improvements in or relating to vegetation cutters, in particular to lawnmowers.

The present invention provides a number of improvements in or relating to lawnmowers, with particular reference to a lawnmower having a deck carrying a motor driven, substantially horizontal, in use, cutter, and supported by four wheels arranged in pairs on respective front and rear axles.

In its broadest aspect, the present invention provides a roller mechanism associated with the rear wheels and a height of cut mechanism of a lawnmower in which the height of the cutter above the ground is adjustable between a low cut position in which a maximum length of grass is removed by the cutter and a high cut position in which a minimum length of grass is removed. The roller is mounted at each end upon a roller carrier mounted, by means of engaging rods, on the chassis of the lawnmower for pivotal movement thereabout. The roller carrier includes a generally hook-shaped feature adapted to engage a corresponding cam surface formed on the pivot arm.

Suitably, the height of cut adjustment mechanism includes a pair of front wheels mounted by means of respective stub axles on respective pivot arms carried on a front axle The pair of rear wheels are similarly mounted on respective stub axles on pivot arms carried on a rear axle. The axles are mounted on the underside of the

chassis and define the points about which the pivot arms pivot. The mechanism includes a link arm pivotally coupled to the front and rear pivot arms on one side of the mower. The link arm is biased into the high cut position by means of a tensioning spring secured between the link arm and the axle. The link arm is held at a selected position by means of a downwardly projecting indexing member provided on the link arm which co-operates with an engaging member pivotally mounted upon the deck or chassis. The engaging member is upwardly biased by means of a spring into engagement with the indexing member Engaging member preferably includes a bent or looped portion which acts as a shock absorbing element.

Actuation of the mechanism is by means of a pivoting, generally inverted Z-shaped, handle located in an aperture at the side of the deck. The handle depresses the engaging member out of engagement with the indexing member when the handle is pivoted upwardly along a generally arcuate path.

In a preferred embodiment, an indicator plate is secured to the front pivot arm As the height is adjusted, the indicator plate rotates with respect to the front of the deck where an indicator marker is provided. The indicator plate is calibrated to display a number corresponding to the height of grass cutting provided through the range of adjustments allowed by the indexing member Alternatively, the marker may be provided on the plate and the numerical scale applied to the deck.

The above and other aspects of the present invention will now be described in further detail, by way of example only, with reference to the accompanying drawings, in which

Figure I is a part cut away plan view of a rotary lawnmower embodying certain aspects of the present invention ; Figure 2 is a part cut away side view of the lawnmower of Figure 1, Figure 3 is a side view of the components of a height of cut adjustment mechanism in accordance with the first aspect of the present invention; Figure 4 is a plan view of the mechanism of Figure 3; Figures 5 and 6 are perspective views illustrating the height adjustment of a lawnmower including the height of cut adjustment mechanism of Figures 3 and 4; Figure 7 is a perspective skeleton view of an adjustable rear roller mechanism in accordance with the present invention, in combination with the height of cut mechanism of Figures 3 and 4 ; Figure 8 is an plan view of the roller mechanism of Figure 7; and Figure 9 is a side view of the roller mechanism of Figures 7 and 9; Referring to Figures 1 and 2, there is shown an embodiment of a lawnmower 10 in accordance with the present invention. The mower 10 includes a deck 11 over a chassis carrying a motor driven cutter 12. The cutter, in use, rotates at high speeds cutting the grass as the mower is pushed along the ground A conventional fan 19 mounted above the cutter develops an air stream which carries the grass cuttings rearwardly towards a discharge chute offset to one side at the rear of the mower. A handle 13 is mounted upon the deck 11. The mower has a pair of front wheels 14 mounted by means of respective stub axles 17 on respective pivot arms 15 carried on a front axle 16. A pair of rear wheels 20 are similarly mounted on respective stub

axles 21 on pivot arms 22 carried on a rear axle 23. Axles 16, 23 are mounted on the underside of the chassis and define the points about which the pivot arms 15,22 pivot.

By way of introduction, with additional reference to Figures 3 and 4, an example of a height of cut adjustment mechanism is illustrated and includes a link arm 25 pivotally coupled to the front 15 and rear 22 pivot arms on one side of the mower If link arm 25 is moved generally to the left and right as shown in Figure 3, it will be apparent that pivot arms 15, 22 will be caused to pivot about the axles 16 thus adjusting the height above the ground of the wheel stub axles 17,21 with respect to the axles 16,23 which are mounted on the chassis. As the link arm 25 is moved towards the rear of the mower (in the direction of arrow A in Figure 3), the wheels will be raised with respect to the chassis thus producing a closer cut, whereas if the link arm 25 is moved towards the front of the mower, the wheels will be lowered, leaving the cut grass longer. The link arm 25 is biased into the high cut position by means of a tensioning spring 26 secured between the link arm 25 at a convenient, generally central, position on a wing 27, and a suitable position on the axle or chassis.

The link arm 25 is held at a selected position, and thus the wheels at a selected

height, by means of a downwardly projecting radiussed indexing member 28 01 1- provided on the link arm 25 which co-operates with an engaging member 29 pivotally mounted on a support 30 attached to the deck l l of the mower 11 The

engaging member 29 is upwardly biased by means of a spring 31 into engagement 1. 71 1. 1

with notches 32 of the indexing member 29. Engaging member 29 includes a bent or looped portion 33 which acts as a shock absorbing element This is advantageous in the event that the mower is dropped. As the link arm 25 is directly attached to the wheels, any impact on the wheels could be transmitted through the engaging member to the deck which could result in damage to the height of cut mechanism linkage. The loop 33 tends to absorb any impact forces and recover thus avoiding damage.

Adjustment of the height of cut mechanism is by means of a pivoting, generally inverted Z-shaped, handle 34 located in an aperture at the side of the deck II. The handle 34 pivots about a point 35 and simply depresses the engaging member 29 out of engagement with the indexing member when the handle is pivoted upwardly along a generally arcuate path. The adjustment can then be easily made by the user, either allowing the biasing spring 26 to cause the deck to rise with respect to the wheels or, by exerting a little pressure on the deck, encouraging the wheels to rise with respect to the deck. Conveniently, a hand grip 36 is provided at the rear of the mower and a palm rest 37 is provided on the upper surface of the deck.

In the embodiment shown, an indicator plate 38 is secured to the front pivot arm 15. As the height of cut is adjusted, the indicator plate 38 rotates with respect to the front of the deck I I where an indicator marker 39 is provided. The indicator plate is calibrated to display a number corresponding to the height of grass cutting provided through the range of adjustments allowed by the indexing member 28.

Alternatively, the marker may be provided on the plate 38 and the numerical scale applied to the deck. With reference to Figures 12 to 14, in accordance with the present invention, the lawnmower is fitted with a roller 60 associated with the rear wheels 20 and adjustable therewith by means of the height of cut mechanism as described above or other, prior art height of cut mechanisms. The roller 60 is mounted at each end upon a roller carrier 61 mounted, by means of engaging rods 62, on the chassis of the lawnmower for pivotal movement thereabout The roller carrier 61 includes a generally hook-shaped feature adapted to engage a corresponding cam surface formed on the pivot arm 22. As will most readily be seen from Figure 14, as the link arm 25 moves to the left (as viewed from the Figure) the cam surface of the pivot arm 22 will engage the roller carrier 61 causing it to pivot about the position of rod 62 thereby causing the roller to move downwardly as the wheel moves in the same sense to ensure that the roller maintains contact with the ground

Claims

Claims I. A roller assembly associated with the rear wheels and a height of cut mechanism of a lawnmower having a chassis and a pair of rear wheels mounted on respective stub axles on pivot arms carried on a rear axle ; the axles being mounted on the underside of the chassis and defining points about which the pivot arms pivot ; wherein the roller is mounted at each end upon a roller carrier mounted, by means of engaging rods, on the chassis of the lawnmower for pivotal movement thereabout : wherein the roller carrier includes a generally hook-shaped feature adapted to engage a corresponding cam surface formed on the pivot arm.
2. A lawnmower roller assembly substantially as herein described with reference to Figures 7 to 9.
3. A lawnmower comprising a roller assembly as claimed in claim I and including a height of cut adjustment mechanism, in which the height of the grass cutter above the ground is adjustable between a low cut position in which a maximum length of grass is removed by the cutter and a high cut position in which a minimum length of grass is removed; wherein the lawnmower has: a pair of front wheels or rollers mounted by means of respective stub axles on respective pivot arms carried on a front axle, and a pair of rear wheels similarly mounted on respective stub axles on pivot arms carried on a rear axle; the axles being mounted on the underside of the chassis and defining points about which the pivot arms pivot;

wherein the height of cut adjustment mechanism includes a link arm pivotally coupled to the front and rear pivot arms on one side of the mower, the link arm being biased into the high cut position by means of a tensioning spring secured between the link arm and the axle; wherein the link arm is held at a selected position by means of an indexing member associated with the link arm which co-operates with an engaging member associated with the deck or the chassis; and wherein the engaging member is biased by means of a spring into engagement with the indexing member.
4. A lawnmower as claimed in Claim 3 wherein the engaging member includes a bent or looped portion which acts as a shock absorbing element.
5. A lawnmower as claimed in Claim 3 or Claim 4 wherein actuation of the mechanism is by means of a pivoting, generally inverted Z-shaped, handle located in an aperture at the side of the deck; wherein the handle depresses the engaging member out of engagement with the indexing member when the handle is pivoted upwardly along a generally arcuate path.

6 A lawnmower as claimed in any one of Claims 3 to 5 further comprising an

indicator plate is secured to the front pivot arm ; wherein as the height is adjusted, im the indicator plate rotates with respect to the front of the deck to thereby display a number corresponding to the height of grass cutting provided through the range of adjustments allowed by the indexing member.

7 A lawnmower substantially as herein described with reference to Figures I to
6.