TECHNICAL AREA

This invention concerns an arrangement intended to be mounted at a vehicle that comprises a load- bearing part and driving wheels. The invention concerns also a vehicle comprising such an arrangement.

BACKGROUND

Vehicles, machines, agricultural machines and forestry machines have long been used within forestry in order to automate many of the operations that are to be carried out on location in a forest. The vehicles have a weight that is not insignificant, independently of whether they are driven with the aid of wheels or tracks, which means that the forest, the support of the vehicle in the forest, the ground, over which the vehicle is driven and on which it stands, is affected. The ground is compressed by the weight of the vehicle and the damage to the ground may be permanent in the form of damage that does not recover without intervention. This damage to the ground may result in erosion, leakage of humus and nutrients, the unplanned formation of ditches, and compression of the pore system of the ground, all of which may have consequences. All such consequences affect the remaining forest, through, for example, lower resistance to storms due to roots that are torn off and/or thick roots that are shallow, to increased root rot as a consequence of root damage, and to loss of growth. Once the damage has taken place, all attempts to restore the ground are expensive, or totally impossible. Repair of damage caused by driving is most often of a cosmetic nature. Up to half of the support capacity of the ground arises from the roots. The support capacity is, therefore, difficult to restore when the vegetation and root systems have been broken. Furthermore, repair by, for example, the use of an excavator means that the ground is excavated one more time. This increases further the risk for the undesired transport of slurry, humus, nutrients and heavy metals into lakes and watercourses. For these reasons, the damage caused by driving should be attempted to be prevented as far as possible.

In order to avoid damage to the ground and damage caused by driving, a great deal of time has been invested in planning appropriate routes, passages and collection points well in advance of a felling operation. This is not only time-consuming but also expensive. The compression of the ground by the weight of the vehicle can lead also to the driving of the vehicle becoming more difficult.

SUMMARY OF THE INVENTION

One purpose of the present arrangement is to reduce the influence on the forest from a vehicle, on the support of a vehicle in the forest, on the ground, where the vehicle is driven or allowed to stand. This purpose is achieved with an arrangement comprising the technical features that are made clear by claim 1. This purpose is achieved also with a vehicle comprising such an arrangement according to claim 13.

DESCRIPTION OF DRAWINGS Figure 1 shows a vehicle and an arrangement according to the invention. Figure 2 shows the vehicle and the arrangement in Figure 1 from above.

Figure 3 shows a second embodiment of a vehicle and an arrangement according to the invention. Figure 4 shows the vehicle and the arrangement in Figure 3 from above. Figure 5 shows an auxiliary motor comprised in an arrangement according to the invention. Figure 6 shows a damping arrangement comprised in an arrangement according to the invention. Figure 7 shows a tension arrangement comprised in an arrangement according to the invention.

DESCRIPTION OF EMBODIMENTS

This invention concerns an arrangement 1 intended to be mounted at a vehicle 2. The vehicle 2 comprises a load-bearing part 3 and driving bogie wheels 4.

The arrangement 1 comprises at least two extra wheels 5 that can be individually controlled, where each extra wheel 5 is arranged at a fixed, non-rotatable, pivotable, shaft 6. At least one bogie wheel 4 is arranged at, fixed at, a bogie box 7. Also the extra wheel 5 is arranged at, fixed at, the bogie box 7 in order to distribute the weight of the machine, the gross weight of the machine including its payload weight, over more areas of a support 8, the ground, and in this way improve the distribution of weight and reduce the pressure against the support, the ground. The extra wheels 5 give a direct support and a supplementary ability to distribute the weight, in addition to the normal vehicle wheels 4. See Figures 1-4.

The term "individually controlled extra wheels 5" is here used to denote that each extra wheel, independently of its location on the vehicle 2, can be controlled and adjusted and can follow the support 8, without being influenced by, and without influencing, other extra wheels and their locations. It is possible also that two extra wheels 5 be located on the same side of the vehicle 2, if this is required in special terrain. It is possible also that more than two extra wheels 5 be mounted at a vehicle. The individually controlled extra wheels 5 are subject to a driving force. The driving force on the wheels further facilitates the driving of the vehicle 2 on the support, and since the extra wheels 5 are driven and move relative to the support, the extra wheels 5 will be in motion and will not become as easily stuck in such material as is located on the support 8, such as, for example, vegetation.

The individually controlled extra wheels 5 may be hydraulically driven or electrically driven. It is appropriate that the arrangement 1 comprise an auxiliary motor 9 that drives each extra wheel 5. The motor 9 is driven by a hydraulic system comprising a pump 10. The pump 10 is driven by an additional source of energy 11, such as, for example, a diesel engine, electric motor or similar. See Figure 5.

The arrangement 1 comprises at least two arms 12 on which an extra wheel 5 is mounted. Each arm 12 is individually controlled and mounted in bearings, and can move independently of the motion of the other arm. Each arm 12 is principally mounted in bearings in a horizontal axis 13 that essentially coincides with the closest wheel 4a of the bogie and its wheel axle, in order to permit the extra wheel 5 to be lifted up and down without the axle separation between the closest wheel 4a of the bogie and the extra wheel 5 changing by any amount worthy of mention.

Each arm 12 comprises a damping arrangement 14 that damps the motions of the arm. It is appropriate that the damping arrangement 14 of the arm comprise a damped cylinder that retains, presses, the extra wheel 5 against the support 8 in order to ensure that the extra wheel 5 is in contact with the support 8 and in this way improve the distribution of weight and reduce the pressure exerted by the vehicle 2 onto the support 8, the ground. The damping arrangement, the damped cylinder 14, is controlled by a hydraulic unit 15 that is fed by a hydraulic pump 16 that obtains its energy from a selected source of energy 17, such as, for example, an electric motor, a diesel engine or other source of energy or source of driving power. The damping arrangement, the damping cylinder 14, comprises an accumulator 18 that offers a spring facility and that can store energy for a short period. See Figure 6.

The arrangement 1 comprises a track 19 that protects against skidding, distributes the weight, and reduces ground pressure. This track 19 is located around each set of bogie wheels 4 and the extra wheel 5. See Figures 1 and 3.

Two extra wheels 5 are arranged at at least two bogie boxes 7, one on each bogie box 7, arranged to be parallel one on each side of the vehicle 2, one extra wheel 5 at one of the two bogie wheels 4 in the forwards and/or backwards direction of the vehicle 2 one on each side of the vehicle 2. See Figures 1 and 2. A further alternative is that four extra wheels 5 are arranged at at least two bogie boxes 7 arranged to be parallel one on each side of the vehicle 2, one extra wheel 5 at each bogie wheel 4 in the forwards and backwards direction of the vehicle 2. See Figures 3 and 4.

The arrangement comprises a tension arrangement 19 in the form of a spring-loaded arrangement, such as a cylinder under pressure or a coiled spring unit, in order to absorb motions along the length of the arm 12 such that the length of the track, and its tension, do not change when the arm 12 moves up and down. See Figure 7.

The invention concerns also a vehicle 2 comprising an arrangement 1 of the type that has been described above. The load-bearing part 3 of the vehicle comprises a conventional load-bearing frame. The load-bearing part may comprise also a separate displaceable load carrier. The driving wheels 4 of the vehicle comprise a mechanically driven, a hydraulically driven, or an electrically driven bogie. See Figures 1-7.

The vehicle 2 is intended to be used within forestry or agriculture since it is within these fields of use that it is economically and biotopically interesting that damage to the ground is avoided or at least minimised. Other fields of use in which damage to the ground should be avoided or at least minimised may, of course, become relevant.