GB2367475A

GB2367475A - Lawnmower height adjustment

Info

Publication number: GB2367475A
Application number: GB0120242A
Authority: GB
Inventors: Andrew Quigley
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2000-08-31
Filing date: 2001-08-20
Publication date: 2002-04-10
Anticipated expiration: 2021-08-20
Also published as: GB0021426D0; DE10142072B4; GB0120242D0; DE10142072A1; GB2367475B

Abstract

A lawncare machine, such as a lawmower or a scarifier, has front 10a,10b and rear 10c,10d wheels joined by respective front 11 and rear 12 axles, the axles being connected to one another by a linkage 25. The linkage 25 comprises a single component pivotally connected at each end to respective links 13,14 having openings 16,15 for receiving the front and rear axles 11,12. The componenf 25 includes an integral arm 16 providing a detent that is releasably engagable with a detent mechanism 28 in a plurality of alternative positions to vary the height of a working tool above the ground. The link 25 deforms laterally to allow engagement and disengagement of arm 26. If the machine is excessively loaded, for example by dropping, link 25 will deform and arm 26 will disengage thus protecting the mechanism from damage.

Description

LAWNCARE MACHINES This invention relates to a mechanism for changing the height-of cut on a lawncare machine such as, for example, a rotary lawnmower or a scarifier, where a working member is driven at different preselected heights above the ground.

To change the height-of-cut on a rotary lawnmower, for example, the groundengaging wheels or rollers must be raised or lowered relative to the deck that supports the motor or engine driving the rotating cutting element.

In one known arrangement, the mower includes front and rear axles connected by a link, and either the link itself or one of the front/rear axles is then connected to the deck, for example by means of an additional lever which can be engaged with the deck in a number of alternative positions.

According to one aspect of the present invention there is provided a lawncare machine having front and rear wheels joined by respective front and rear axles, the axles being connected to one another by a linkage, the linkage comprising a single component pivotally connected at each end to respective links having openings for receiving the front and rear axles, the component including an integral arm providing a detent that is releasably engageable with a detent mechanism in a plurality of alternative positions to vary the height of a working tool above the ground.

The single component is preferably flexible such that disengagement of the detent is achieved by manually flexing, twisting or deforming the component. The detent arm preferably extends upwardly from the component such that lateral deflection of the arm exerts a torque on the component while disengaging the detent from the detent mechanism. The component may also be deformable from a normally straight configuration into a curved configuration in response to the lateral deflection of the detent arm.

Disengagement of the detent may also occur if a dynamic load transmitted to the single component of the linkage from the front and rear axles exceeds a predetermined level.

By way of example only, a lawnmower embodying the invention is illustrated in the accompanying drawings wherein: Fig. 1 is a schematic view of the height-of-cut adjustment mechanism for a rotary lawnmower viewed from one side of the mower, and Fig. 2 is a schematic view corresponding to Fig 1 but viewed from the opposite side and opposite end of the mower.

For clarity, only the essential components of the height-of-cut adjustment mechanism are illustrated, and the remainder of the mower, including the deck, drive motor and cutting element, would be conventional. In particular the mower would include a drive motor supported on the deck and driving the cutting element for rotation about a vertical axis beneath the deck. The mower would also include an upright handle connected to the deck for manoeuvring the mower over the ground.

Referring to the drawings, the mower includes two front wheels lofa, 10b, and two rear wheels 1 Oc, I Od. The front wheels are joined by a front axle 11, and the rear wheels by a rear axle 12.

The opposing ends of the front axle 11 are cranked, the crank at the left hand end (as viewed in Fig. 1) being accommodated in a slot 15 of a generally triangular front connecting link 13. Similarly, the opposing ends of the rear axle 12 are cranked and the crank at the left hand end (as viewed in Fig. 1) is accommodated in a slot 16 of a generally L-shaped rear connecting link 19 The apex of the triangular front link 13 and of the L-shaped rear link 19 are then pivotally connected to opposed ends of an interconnecting link 25 which joins the front and rear axles. The interconnecting link 25 includes an integral upright arm

26 positioned about one third of the distance from the rear end of the link and providing a detent of a detent mechanism, the detent arm 26 including notches 27 that engage with corresponding notches 28 disposed along one side of an elongate slot 29 in a fixed part 30 of the mower such as the deck. To disengage the detent arm 26 from the detent mechanism, the arm 26 is laterally displaced away from the notches 28. This lateral movement is accommodated by the link 25 twisting in response to the applied torque and/or by the link 25 deforming from its normally straight configuration into a slightly curved or bowed configuration. Once disengaged, the arm 26 can be moved along the slot 29 in either a forward or reverse direction so that the front and rear connecting links 13,19 rotate in a clockwise or anticlockwise direction to raise or lower the front and rear wheels relative to the axles 11 and 12, thereby adjusting the height-of-cut. The detent arm 26 is then released and re-engages with the notches 28 of the detent mechanism.

The adjustment mechanism also includes a counterweight spring 31 which has one end connected to the base of the detent arm 26 and its other end connected to a point on the deck. Accordingly, when the detent arm 26 is released from engagement with the notches 28, the static load on the front and rear axles that is transmitted to the link 25 is counterbalanced by the spring 31 while moving the detent arm to its new position in the slot 29.

If the mower is excessively loaded, for example, by dropping it on all four wheels, the link 25 will deform, twist or flex in such a manner as to disengage the detent arm 26 from the notches 28, and the deck will then fall to its lowest height-of cut position. Further movement of the deck beyond the lowest height-of-cut position could be provided so that the wheels or axles contact the deck or some other part of the mower structure directly under extreme loads. In this manner, the adjustment mechanism is protected from damage due to such excessive loads.

One advantage of the illustrated mechanism is its simplicity and by using an integral part of the connecting link 25 as a detent to releasably engage the deck it requires fewer components than previous adjustment mechanism.

Essentially the same adjustment mechanism could be used with other lawn care machines, such as lawn scarifiers, to adjust the height of a working member which is driven at different heights above the ground.

Claims

CLAIMS : 1. A lawncare machine having front and rear wheels joined by respective front and rear axles, the axles being connected to one another by a linkage, the linkage comprising a single component pivotally connected at each end to respective links having openings for receiving the front and rear axles, the component including an integral arm providing a detent that is releasably engageable with a detent mechanism in a plurality of alternative positions to vary the height of a working tool above the ground.
2. A lawncare machine according to claim 1 wherein the said component of the linkage is flexible such that disengagement of the detent is achieved by manually flexing, twisting or deforming the said component.
3. A lawncare machine according to claim 2 wherein the detent arm extends upwardly from said component of the linkage such that lateral deflection of the detent arm exerts a torque on the said component while disengaging the detent from the detent mechanism.
4. A lawncare machine according to claim 2 in which the said component of the linkage is deformable from a normally straight configuration into a curved configuration in response to a lateral deflection of the detent arm to disengage the detent from the detent mechanism.
5 A lawncare machine according to claim 2 wherein disengagement of the detent is further achieved if a dynamic load transmitted to the said component of the linkage from the front and rear axles exceeds a predetermined level.
6 A lawncare machine according to any one of the preceding claims in which the front and rear axles are cranked at each end, the said front and rear links pivotally connected to the said component of the linkage each having a slot for accommodating

a respective one of the cranked ends of the front and rear axles, whereby forward and backward movement of the said component rotates the front and rear connecting links in a clockwise or anticlockwise direction to raise or lower the front and rear wheels relative to the front and rear axles.
7. A lawncare machine according to any one of the preceding claims wherein, with the detent released from the detent mechanism, the static load on the front and rear axles transmitted to the said component of the linkage is counterbalanced by a resilient biasing force acting on the detent arm
8. A lawncare machine according to any one of the preceding claims wherein the working tool is a grass cutting device.
9. A lawncare machine according to any one of the claims 1-7 wherein the working tool is a scarifier,
10. A lawncare machine according to claim 1 and substantially as herein described with reference to the accompanying drawings