GB2424630A

GB2424630A - Vehicle with adjustable track width

Info

Publication number: GB2424630A
Application number: GB0506388A
Authority: GB
Inventors: Graham Smith
Original assignee: HOUSEHAM SPRAYERS Ltd
Current assignee: HOUSEHAM SPRAYERS Ltd
Priority date: 2005-03-30
Filing date: 2005-03-30
Publication date: 2006-10-04
Also published as: GB0506388D0

Abstract

A vehicle such as an agricultural sprayer vehicle has a chassis (1) mounting front and rear axles (5) each carrying a pair of wheels (10), the axles being selectively extendible and retractable in order to change the vehicle track width. At least one pair of wheels (10) is pivotally mounted on the respective axle (5) and provided with linkages (16a, 17) to a steering arm (16b) mounted on a carriage (14) mounted so as to move longitudinally of the chassis as the axles are extended or retracted, whereby the geometry of the wheels relative to the vehicle and to each other does not change as a result of the extension or retraction. The wheels are moved by an hydraulic cylinder in which fluid is supplied through a bore through the piston rod.

Description

VEHICLE WITH ADJUSTABLE TRACK WIDTH

Field of the Invention

This invention relates to a vehicle with adjustable track width, for example an agricultural sprayer vehicle whose track needs to be adjusted to accommodate different crop row widths.

Background to the Invention

Agricultural sprayer vehicles need to be able to pass over growing crops without damaging the crop. The track or lateral wheel spacing needs to be such that the wheels pass between the rows of crop where possible. However, because the spacing of crop rows is not always the same, it is desirable to be able to change the vehicle track to accommodate the different crop plantings, so as to maximise the use of the vehicle. With some vehicles, this has been achieved by the use of different-sized axle extenders or spacers, but changing from one track width to another is a laborious and time-consuming process, reducing the general availability of the sprayer.

1 5 There have been various proposals for vehicles which can change their track width without the need to take the vehicle out of operation. For example, GB-A-2 311 967 discloses a vehicle using hydraulically-extendible and retractable axles to change the track width, and with mechanical linkages to maintain steering control. While this avoids the need to perform mechanical work on the vehicle every time the track width is to be changed, a disadvantage of this arrangement is that, as the track is adjusted, the wheelbase - the longitudinal distance between the two sets of wheels - changes. For some circumstances, this can have an adverse effect on the stability of the vehicle, particularly since sprayer vehicles are designed to carry extended spraying booms.

In US-A-5 489 11 3, a vehicle is disclosed which avoids the problem of changeable wheelbase with track by relying on independent hydraulic steering of the individual wheels. Hydraulic steering is considered unacceptable for many applications, because a sudden hydraulic failure can result in rapid destabilisation of the vehicle, with consequent risk of an accident.

EP-A-0 501 585 discloses a vehicle having, in effect, two separate chassis halves with a hydraulic cylinder between them to urge them apart or bring them closer together. The wheelbase is fixed by mounting the wheels on a longitudinal beam

Specification HOUSEHAMP1 287.GBA 2005-03-29.doc

constituting the main part of the chassis half. The vehicle body is mounted so as to float over the chassis, to allow the chassis halves relative movement. This means that the support for the vehicle body is dependent on a pivoting connection to the chassis, and is thus less stable than a fixed chassis.

It is therefore desirable to provide a vehicle having a fixed chassis, mechanical linkage steering, and the ability to vary the track width without changing the wheelbase.

Summary of the Invention

Accordingly, the invention provides a vehicle having a chassis mounting front and rear axles each carrying a pair of wheels, the axles being selectively extendible and retractable in order to change the vehicle track width, at least one pair of wheels being pivotally mounted on the respective axle and provided with linkages to a steering arm mounted on a carriage mounted so as to move longitudinally of the chassis as the axles are extended or retracted, whereby the positions of the wheels relative to the vehicle and to each other do not change as a result of the extension or retraction.

1 5 Preferably, movement of the carriage is controlled by at least one hydraulic cylinder, and more preferably by a pair of such cylinders arranged to allow their pistons to float. Valves may be provided to lock the cylinder or cylinders when the extension or retraction of axles has ceased.

The axle ends are preferably each provided with a torque arm pivotally connected thereto and to the carriage, to maintain vertical rigidity of the wheels.

The axles have two relatively slidable parts, and may be extended and retracted by a respective hydraulic cylinder therebetween. In order to ensure that the axles are extended and retracted equally on both sides of the vehicle, a mechanical linkage such as a Watts linkage may be provided on each axle between the two relatively slidable parts thereof.

The axles are preferably each carried by a swinging arm frame mounted on a pivot fixed to the chassis. This allows for springing and shock absorbers to be provided between the axles and the chassis, if required. A rubber spherical bearing is preferably used for mounting the swing arm frame on the chassis.

Drive for the vehicle is conveniently provided by hydraulic motors on each wheel.

Specification HOUSEHAMP1 287.GBA 2005-03-29.doc

The configuration permits the vehicle track width to be adjusted infinitely between its two extremes whilst the vehicle is moving. While the vehicle may be used as a sprayer for agricultural use, the invention is applicable to other types of vehicle which may need to vary the track width without changing the wheelbase.

Brief Description of the Drawings

In the drawings, which illustrate an exemplary embodiment of the invention: Figure 1 is a plan view of the chassis and axle assemblies of a vehicle in accordance with an embodiment of the invention, one axle being in the fully retracted configuration thereof and the other being in the fully extended configuration; Figure 2 is a plan view of one axle assembly in the fully extended configuration; Figure 3 is a view corresponding to that of Figure 2, but with the axle fully retracted; Figure 4 is a perspective view from below and to one side of the swinging arm/axle assembly; 1 5 Figure 5 is an underneath plan view of the assembly shown in Figure 4; and Figure 6 is an enlarged sectional view of the axles showing the arrangement of the hydraulic cylinder therein.

Detailed Description of the Illustrated Embodiment

The sprayer vehicle of the illustrated embodiment has a chassis 1 consisting of a rectangular frame on which the driver's cab and spray equipment are mounted, the frame having generally centrally thereof two laterally extending support members 2, each carrying a spherical rubber bearing 3 from which is pivoted a swinging arm frame 4. The frame 4 includes two main frame members 4a set at an oblique angle to the longitudinal axis of the vehicle and connecting at the free ends thereof to an axle 5 of hollow tubular construction, with two relatively slidable extension members 6 and 7 therein connected to a hydraulic cylinder 8. The extension members 6 and 7 are attached at their free ends to a respective pivoting wheel support bracket 9, in which is mounted a hydraulic motor (not shown) driving a wheel 10. The wheel mounting brackets 9 extend downwardly from the chassis so as to extend the vertical clearance of the chassis over the crop, in use.

Each swinging arm main frame member 4a is connected to the other at the end adjacent to the pivot bearing 3 by a pair of lateral cross-members 11, together

Specification HOUSEHAMP1 287 GBA2OO5-O3-29.doc

supporting a horizontal longitudinally-extending hydraulic cylinder 12 at each end thereof. The cylinders 12 each have their piston rod 1 3 connected to a carriage 14 which can be moved longitudinally of the chassis by the cylinders 1 2. The carriage 14 consists of a pivot block 1 4a at each side of the chassis with a linking arm 1 4b therebetween. Each pivot block 14a pivotally mounts one end of a respective torque arm 1 5, the opposite end of each torque arm being pivotally connected to a respective one of the wheel support brackets 9. The torque arms 1 5 are suitably fabricated as tapering channel-section beams for rigidity and minimum weight.

The pivot blocks 1 4a also carry a steering lever assembly 1 6, consisting of two cranks 1 6a each pivotally connected to a respective one of the pivot blocks 1 4a and linked together by a transverse steering rod 1 6b connected at its mid- point to a double- acting hydraulic cylinder 1 6c mounted on a fixed cross-member 1 6d extending between the pivot blocks 1 4a. Hydraulic pressure applied to one side of the cylinder 1 6c causes its displacement relative to the cross-member 1 6d, in turn rotating the cranks 1 6a. The 1 5 motion of the cranks is transmitted to the wheel support brackets 9 through steering arms 17 connected thereto via suitable flexible bushes 18, and similarly connected at their other ends to pivot mountings 1 9 on the wheel support brackets 9 offset from the rotational pivot to provide a steering action. With the steering directed straight ahead, the pivot points for the steering arms 17 and the pivot points for the torque arms 1 5 are on substantially the same axes as each other at the respective ends so that they follow the same geometry during widening and narrowing of the vehicle track.

It will be seen that, although steering is effected by a hydraulic cylinder, in the event of failure of the hydraulics, the wheels are rigidly linked together and cannot therefore steer in different directions compromising stability of the vehicle.

A Watts linkage 20 is mounted on the axle 5 and is linked at each end thereof to a respective one of the mountings for the torque arms 1 5 on the brackets 9 so that, as the hydraulic cylinder in the axle is expanded or retracted, there is uniform outward and inward movement of the wheels on both sides of the vehicle.

The action of the mountings during widening and narrowing of the vehicle track will now be explained with particular reference to Figures 2 and 3. In Figure 2, the wheels are shown fully extended giving, for example, a 3m track. The torque arms 1 5

Specification HOUSEHAMP1287.GBA2OO5-O3-29 doc

and steering arms 17 extend at their maximum angle to the hydraulic cylinders 12, which are fully retracted. When the hydraulic cylinder 8 in the axle is retracted, drawing in the extension pieces 6 and 7 towards a minimum track width of, say, 2m, the pivot points of the torque arms and steering arms move towards each other. If the other ends of the torque arms and steering arms were attached to a fixed pivot point, the movement of the wheel mounting brackets 9 would follow an arc, with the result that the wheelbase would increase as the track decreases, and vice versa. To maintain the wheelbase constant, the cylinders 12 are allowed to float, extending as the track is decreased, and retracting as the track is increased. Thus, the pivot points for the steering and the torque arms move longitudinally of the vehicle during expansion and contraction of the track to maintain a constant wheelbase. Control valves will be provided to control the flow of fluid to and from the cylinders 12. These will open when the axle cylinder 8 is extended or contracted, and close, thereby locking the cylinders 12, when the axle cylinder 8 is at rest.

1 5 The operation of the Watts linkage 20 may also be seen from Figures 2 to 4 in particular, being fully rotated in Figure 3, so that its main arm 20a extends generally longitudinally of the vehicle, and fully extended in Figure 4.

It will be understood that all four wheels could be steerable in the vehicle of the present invention, or it may be sufficient to provide for steering of only one pair of wheels. In the vehicle described with reference to the drawings, all wheels are steerable, but it would be possible to select two-wheel steering or four-wheel steering according to conditions. For example, when travelling on public roads, two-wheel steering will generally be preferable, but for use on some fields over crops, four-wheel steering may provide better control. In arrangements where only one set of wheels is steerable, torque arms may still be desirable for the non-steering wheels, and these will be arranged to move in the same way as for the steered wheels.

Referring now to Figure 6, the hydraulic cylinder 8 within the axle has a cylinder body 60 with a bush 61 at one end for connection to the pivot point for the torque arm on the wheel support bracket. A piston 62 is mounted on the threaded end of a piston rod 63 which is a sliding fit within the end seal 64 in the body 60. The free end of the piston rod 63 carries a bush 65 for connection to the torque arm pivot point on the

Specification HOUSEHAM P1 287.GBA 2005-03-29 doc

opposite wheel. A bore 66 extends axially along the piston road 63 from the free end, where it is closed by the bush, to the threaded portion. A lateral tapping 67 permits fluid to flow between the bore 66 and the body of the cylinder, over the face of the piston. A threaded lateral tapping 68 at the free end adjacent to the bush 65 intersects the bore 66 and permits connection of a hydraulic fluid supply hose. At the opposite end of the cylinder, intersecting bores 69 permIt the supply of fluid from another hose to the interior of the cylinder on the opposite face of the piston. In use, the hoses supplying hydraulic fluid to the cylinder 8 will extend along the torque arms and will conveniently be supported by them.

Specification HOUSEHAMP1 287.GBA 2OO5-O3-29doc

Claims

1. A vehicle having a chassis mounting front and rear axles each carrying a pair of wheels, the axles being selectively extendible and retractable in order to change the vehicle track width, at least one pair of wheels being pivotally mounted on the respective axle and provided with linkages to a steering arm mounted on a carriage mounted so as to move longitudinally of the chassis as the axles are extended or retracted, whereby the positions of the wheels relative to the vehicle and to each other do not change as a result of the extension or retraction.

2. A vehicle according to Claim 1, wherein movement of the carriage is controlled by at least one hydraulic cylinder.

3. A vehicle according to Claim 1 or 2, wherein the axle ends are each provided with a torque arm pivotally connected thereto and to the carriage.

4. A vehicle according to Claim 1, 2 or 3, wherein each axle has two relatively slidable parts.

5. A vehicle according to Claim 4, wherein each axle includes a hydraulic cylinder to extend and retract the axle.

6. A vehicle according to Claim 4 or 5, wherein the two parts of each axle are provide with a mechanical linkage to ensure that the axle extends and retracts uniformly on each side of the vehicle.

7. A vehicle according to Claim 6, wherein the mechanical linkage is a Watts linkage.

8. A vehicle according to any preceding claim, wherein each axle is carried by a swinging arm frame mounted on a pivot fixed to the chassis.

9. A vehicle according to any preceding claim, wherein each wheel is provided with a hydraulic drive motor.

10. A vehicle according to Claim 5, wherein hydraulic fluid is supplied to the one side of the piston in the hydraulic cylinder within the axle from a position adjacent to one wheel through a bore extending through the piston rod.

11. A vehicle substantially as described with reference to, and/or as shown in, Figures 1 to 5 of the drawings.

Specification HOUSEHAM P1 287.GBA' 2005-03-29doc

12. A hydraulic cylinder in which hydraulic fluid is supplied to one side of the piston through a bore through the piston rod.

1 3. A hydraulic cylinder, substantially as described with reference to, and/or as shown in, Figure 6 of the drawings.

Specification HOUSEHAM P1 287.GBA 2005-03-29.doc