GB2068861A - Low ground pressure vehicle - Google Patents

Abstract

A low ground pressure vehicle for use in farming has a front frame section (1) and a rear frame section (2) pivotally interconnected to allow relative angular movement about a first vertical axis (12), and axle on each frame section, and a wheel assembly (7, 10) on each axle the ground engaging surface of which extends across the greater part of the width of the vehicle. Drive means is provided on one or both frame sections for transmitting drive to the axle on that section, and a double acting hydraulic piston and cylinder unit (21) act between the frame sections to steer the vehicle. <IMAGE>

Description

SPECIFICATION Low ground pressure vehicle This invention relates to a low ground pressure vehicle.

With the development and advance of farming techniques it is becoming more desirable to treat fields with fertiliser etc as early in the year as is possible. However, early in the year, the ground in invariably very wet which, by the use of a conventional tractor, results in undesirable compaction of the soil and also reduced traction. In the past, either an extra wheel is bolted to each of the larger rear wheels of the tractor, or a special low ground pressure tractor is used which consists of more than two wheels, usually four, along each side. However, both these arrangements are unsatisfactory particularly since soil damage is caused in turning due to the sliding movement of the extra wheels.

An object of the present invention is to provide an improved low ground pressure vehicle particularly for use in farming.

According to the present invention a low ground pressure vehicle comprises front and rear wheel assemblies the ground engaging surfaces of at least one of which extends across the greater part of the width of the vehicle.

More particularly a low ground pressure vehicle comprises first and second frame sections pivotally interconnected to allow relative angular movement about a first vertical axis, an axle on each frame section, drive means on the first frame section adapted in use to transmit drive to the respective axle on the first frame section, and a wheel assembly on each axle the ground engaging surface of which extends across the greater part of the width of the vehicle.

Preferably the axle on the first frame section is formed in two parts which are rotatable relative to one another and each adapted to receive drive from the drive means. In this arrangement the wheel assembly consists of two wheel units each axle part carrying a separate wheel unit. Preferably the wheel assembly on the axle of the second frame section is also separated into two distinct units rotatable relative to one another but on the same axle. Suitably the first and second frame sections are also relatively angular movable about a second axis perpendicular to and intersecting the first axis.

In the preferred arrangement a hydraulic steering assembly is also provided to transmit steering movement from the first to second frame section.

The invention also includes a high clearance unit in combination with a low ground pressure vehicle for providing a high clearance mode.

The invention will now be described by way of example with reference to the accompanying diagrammatic drawings in which: Figure 1 is a simplified plan view of a first embodiment; Figure 2 is a diagrammatic plan view of a second embodiment; Figure 3 is a side elevation of the embodiment of Fig. 2; Figure 4 is a side elevation of a high clearance conversion unit for the vehicle of Fig. 1 or 2; Figure 5 is a side elevation of the low ground pressure vehicle of Fig. 2 position on the high clearance conversion unit of Fig. 4.

In Fig. 1 of the drawings a low ground pressure vehicle comprises a front frame section 1 and a rear frame section 2 pivotally interconnected at 3. The front frame section 1 includes two co-linear axles 4 and 5 mounted in bearings 6 so that the axles are rotatable relative to one another. Each axle 4 and 5 carries a plurality of tyred wheels 7, which, in each set, may or may not be connected to one another, but which move together. The axles 4 and 5 are suitably of square section.

The rear frame section 2 includes a single axle 8 mounted in bearings 9. The axle 8 carries two sets of a plurality of tyred wheels 10 separated by a spacing collar 11. The axle 8 is suitably of round section so that the wheels of each set and within each set may rotate relative to one another. However, as shown in Fig. 1, the set of wheels of each set are in juxtaposed relationship so that frictional interengagement between adjacent tyres tends to cause the wheels to move together. The pivot connection 3 may be as disclosed in detail with reference to Figs. 2 and 3.

In order to provide a positive steering arrangement for the embodiment of Fig. 1 a double-acting hydraulic cylinder and piston assembly 21 is releasably interconnected between the frame sections by means of knuckle joints 22.

The embodiment of Figs. 2 and 3, in which the same reference numerals have been used for parts corresponding to the first embodiment, comprises a front frame section 1 and a rear frame section 2. The front frame section 1 consists of two co-linear axles 4 and 5, mounted in bearings 6 and on each of which are three spaced low ground pressure wheels 7: a clutch (not shown) may also be provided at the centre mounting for the axles 4 and 5.

However, unlike the first embodiment which is designed to receive a chain or belt drive (not shown) at the outer ends of the axles 4 and 5, the second embodiment is provided with two drive chain sprockets 23 one mounted on each axle inside the respective outermost wheel 7 which each receive chain drive 1 9 from the prime mover positioned over the front wheels 7.

The rear frame section 2 is not provided with low ground pressure tyres 10 across its complete width but is provided with two groups of tyres spaced in the middle so as to provide a mounting position 24 for a fertiliser spinner (not shown) between the two groups.

The spacing 24 enables the spinner to be mounted at the preferred operational height, for proper distribution, of about 20 inches: in the first embodiment the spinner would be mounted behind the rear wheels 1 0.

In both embodiments a prime mover for the vehicle, suitably an internal combustion engine 25, is mounted on the front frame section 1 and the payload, in the form of a spray chemical or fertiliser tank 26, is positioned over the rear wheels 1 0.

As seen from Fig. 3 the pivot connection for both embodiments is suitably arranged so that relative angular movement may take place about two perpendicular axes 1 2 and 1 3. The axis 1 2 allows turning movements to be performed, and the axis 1 3 enables the frame sections to tip one way or the other to accommodate uneven ground during movement.

Suitably, as shown, the pivot connection 3 comprises a rotatable spindle 14, mounted in bearings 15, which defines the first axis 1 2.

Welded to the spindle 14 and extending rearwardly therefrom is a connecting pin 1 6 bolted to the rear frame section 2 at 17, the pin 1 6 defining the axis 1 3. Surrounding the connecting pin 1 6 is a bearing bush 1 8 to accommodate the relative angular movement about the axis 1 3.

In Fig. 4 a high clearance conversion unit 26 is shown which comprises a front frame section 27 and a rear frame section 28. The two frame sections 27 and 28 each have a pair of narrow wheels 29 and 30 respectively and are pivotally connected together at 31 by means of a pivot arrangement corresponding to that described above and for which the same reference numerals have been used. The wheels 29 and 30 support the frame in a high clearance mode giving clearance of about 1 metre.

The front frame section 27 is provided with two pairs of rollers 32 which are rotatably mounted. One of the rollers of each pair is mechanically coupled to the associated wheels through a three to one reduction gear box 33.

The rear frame section 28 is provided with a longitudinally extending track 34 along each side and adjacent each rear wheel 30. In order to steer the high clearance unit the hydraulic assembly of the supported vehicle is dropped down and connected between the front and rear sections 27 and 28 in the same way as between the front and rear sections of the low ground pressure vehicle. Drive is transmitted from the reduction gear boxes 33 to the wheels by means of a respective chain 34 connecting with gear 35 on each wheel 29 (Fig. 5).

A low ground pressure vehicle in accordance with the present invention results in reduced compaction of the soil and increased traction. Also the design provides for high clearance between the sections and less soil damage since turning is not effected by a predominantly sliding movement. As shown it is preferred that several wheels be provided at the front and rear: these may be conventional low ground pressure tyres or discarded road tyres may be used if desired as shown in Fig.

1. On the other hand a single custom made wheel may be used if preferred replacing the plurality of wheels of the set.

If desired either of the embodiments may be provided with a conventional three-point hitch linkage at the rear so that an implement may be towed: this arrangement not only provides low ground pressure but considerable stability, traction being increased by the effect of a trailing implement such as a plough.

In order to convert the unit to a high clearance assembly the low ground pressure vehicle is driven into the conversion unit shown in Fig. 4, for example by driving it up a ramp (not shown). In order to allow the front wheels 7 to pass over the gap between the front and rear sections 27, 28, a removable track (not shown) may be provided at each side as a continuation of the tracks 34. Once in position, as shown diagrammatically in Fig.

5, the front wheels 7 of the low ground pressure vehicle are positioned between rollers 32 and the rear wheels 10 on the tracks 34.

The hydraulic steering assembly is then dropped down as previously described and the vehicle secured in position by suitably connecting means eg: fixing bracket 36 or by chains (not shown). The vehicle is now converted to a high clearance mode and drive is transmitted from the prime mover 25 to wheels 7, through rollers 32 and gearing 33, 34, to the drive wheels 30.

Although the present invention has been particularly described with reference to the engine 25 being mounted over the front wheels, the engine may be provided over the rear wheels if desired. Moreover, in order to drive the vehicle a cab would suitably be provided at 37 although this has been omitted for clarity.

The present invention provides a low ground pressure vehicle for working early in the year without undesirable soil damage.

Once the crop grows it may be converted to a high clearance mode so that a minimum of the crop is flattened by the wheels.

Claims (11)

1. A low ground pressure vehicle comprising front and rear wheel assemblies the ground engaging surface of at least one of which extends across the greater part of the width of the vehicle.

2. A low ground pressure vehicle according to claim 1 wherein the ground engaging surface of the front wheel assembly extends across substantially the whole of the width of the vehicle.

3. A low ground pressure vehicle according to claim 1 or 2 wherein the ground engaging surface of the rear wheel assembly extends across substantially the whole of the width of the vehicle.

4. A low ground pressure vehicle according to claim 1 or 2 wherein the ground engaging surface of the rear wheel assembly is separated into two lateral sub assemblies to provide spacing between said sub assemblies for agricultural spraying equipment.

5. A low ground pressure vehicle according to any one of the preceding claims wherein each of the front and rear wheel assemblies comprises a plurality of wheels.

6. A low ground pressure vehicle according to claim 5 wherein the wheels are spaced apart from one another.

7. A low ground pressure vehicle according to any one of the preceding claims wherein the front and rear wheel assemblies are supported in respective frame sections, the frame sections being pivotally interconnected to allow relative angular movement about a first vertical axis.

8. A low ground pressure vehicle according to claim 7 including drive means on the frame sections adapted in use to transmit drive to the respective wheel assembly.

9. A low ground pressure vehicle comprising first and second frame sections pivotally interconnected to allow relative angular movement about a first vertical axis, an axle on each frame section, drive means on the first frame section adapted in use to transmit drive to the respective axle on the first frame section, and a wheel assembly on each axle the ground engaging surface of which extends across the greater part of the width of the vehicle.

10. A low ground pressure vehicle according to claim 9 wherein the axle on the first frame section is formed in two parts which are rotatable relative to one another and each adapted to receive drive from the drive means.

11. A low ground pressure vehicle according to claim 9 to 10 wherein the first and second frame sections are angularly movable about a second axis perpendicular to and intersecting the first axis.

1 2. A low ground pressure vehicle according to claim 9, 10 or 11 including a hydraulic steering assembly for transmitting steering movement from the first to the second frame section.

1 3. A high clearance vehicle including a low ground pressure vehicle in accordance with any one of claims 1 to 1 2 and high clearance conversion unit, said unit comprising a frame supporting the low ground pressure vehicle, said frame having first and second sections pivotally connected to one another, and two or more wheels on each frame section for supporting the frame at a height providing a high clearance requirement, the first and second frame sections receiving respectively the front and rear wheel assemblies of the low ground pressure vehicle so that drive is transmitted from the driving wheel assembly of the low ground pressure vehicle to the drive wheels of the unit.

1 4. A high clearance vehicle according to claim 1 3 wherein drive is transmitted through two pairs of rollers on one of the frame sections of the high clearance conversion unit.

1 5. A low ground pressure vehicle substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

1 6. A high clearance vehicle according to claim 1 3 substantially as hereinbefore described with reference to the accompanying drawings.