Background to the invention:

The invention applies to a grader, particulary f r use with tractors, for levelling, planing and smoothing running tracks, roads and the like.

Known equipment is described in the introduction to Claim of Patent 1.

Different types of grader are known with levelling blades and smoothing drums. The disadvantages with these are poor penetration characteristics on hard surfaces, lump formation, or poor levelling and unsa isfa tory removal of any vegetation residue.

Purpose of the invention: The main purpose of the invention is to devise a grader which has better operational characteristics than any equivalent, known equipment. It is important that the grader should be suitable for use on relatively hard surfaces, such as gravel tracks and other areas covered by gravel .

Principle of the invention:

The principle of the invention is described ir. the charac erizing part of Claim of Patent 1. Other useful features, which are not obligatory, are stated in Ciaims cf Patent 2 - 5.

Examp1e:

The invention is described below in more detail with reference to the heavily schematic drawings, where Fig. 1 illustrates a detail from a cross-section of a grader designed in accordance with the invention, and attached to a tractor, while

Fig. 2 shows a horizontal section from above the grader in Fig. 1. The grader in the example consists of a forward leveller blade 11, linked to a pair of braces 12 which are pressed towards the surface by a pair of helical springs 13 attached to the braces. The braces 12 are firmly attached to a square cross-beam 14 which has an adjustable support-wheel 15 at each end. The braces 12 extend forwards and downwards m relation to the cross ^¬ beam 14.

The cross-beam 14 is equipped with three anchorage points for a three point suspension on a tractor. Only the upper of these is shown at the leading eάge of an arr; 16 which is supported by a pair of upward protruding struts 17 attached to the cross-beam 14. The struts support a gearbox 18 which is designed to be connected t: the tractor's power supply. The gearbox 18 has a downward protruding axle 19 whici". is connected to a pivot 20. The pivot 20 is linked by joints at each end to front and back transverse rails, 21 and 22 respectively, which each m turn support a row of downward protruding teeth or the "toothed blades" 23 and 24. The transverse rails 21 and 22 are locked together ir. a hinged parallelogram with two more jointed pivots 25 and 2S. one on each side cf the central drive iv : 21 ^" . Pivots 25 and 26 are hinged on the cross-bear;, 14. The details of this are not illust ated.

The toothed blades 23 and 24 are mounted so as t harrow the surface after it has been planed by the leveller blaαe 11. The harrowing is ign i antly

intensified by the lateral movement or vibration that comes from the drive pivot 20.

The cross-beam 14 supports a pair of backward-facing supports 27 and 28 which are attached to a smoothing blade 29 with a runner-shaped cross-section.

On the back transverse rail 22, there is a pair of backward-f cing supports 31 and 32 which are hung on tv/o upward protruding ϋ-brackets 30. Supports 31 and 32 carry a lateral harrow 33, i.e. , a rail 34 with downward protruding teeth 35.

The teeth 35 correspond to the toothed blade in shape and distribution but may have different dimensions. The harrow 33 is designed to be positioned diagonally in relation to the tractor's direction of travel. This means that the mass which does not pass through the teeth 35 is led towards the backward end of the row of teeth.

Since it is mounted on the back transverse rail 22, the harrow 33 will swivel sideways with the rail . This will increase the effect of the sifting so that the teeth 35 do not become clogged by the mass which is small enough to pass through. At the same time, objects which are too large to pass through, e.g. , plant roots, will be forced towards the side.

A brush could be fitted behind the harrow 33 which would even out the surface before it is smoothed by the smoothing blade 29.

The various blades could be fitted so that they are adjustable, this will ensure that their height and angles are suitable for specific areas of use. As an alternative, the smoothing blade 29 could be replaced by a roller.

It is important that the grader in this inventie ha-' two parallel laterally-vibra ing rows of toothed b ades 23 and 24. This counterbalances the lateral forces whicr: would have otherwise been transferred tc the tracts. . I:\ addition, two rows of teeth working in opposition is ∑_ more effective means of crushing or pulverising luir.j: .- than one rev? of lateral iy-v bratH D teeth, cr tw : ιx :.

rows of teeth.

The toothed blades 23 and 24 may have be of different design, density and length depending on the area of use. It could be advantageous to set the teeth in the trailing row 24 slightly lower than those in the leading row, so as to counterbalance the lateral forces as much as possible. The return force from the surface will result in oscillations in the supports, which will cause vibration. This vibration will in turn be transferred to the smoothing blade 29 thereby increasing its effect.