The present invention relates to a device for working the ground comprising a frame with a plurality of standing shafts mounted pivotally thereon, moveable setting means connected with said shafts for collectively pivoting said shafts, each said standing shaft being provided on a free end with a lying shaft whereon a disc-shaped body is rotatably mounted in a bearing, wherein each disc-shaped body has a concave and a convex side, and adjacent disc-shaped bodies are arranged in parallel relationship. Such a device is known from the US Patent No. 3,675,725.

Such a device (normally known as a disc harrow) is used in agriculture for further working of ploughed earth, for ploughing under seed and manure and/or for weed control. It is of great importance in the said workings to keep the working depth, i.e. the depth to which the discs work the ground, substantially unchanged. A disc harrow is generally fixed for this purpose to a so-called three-point lifting device that forms part of a tractor and with which the position of the harrow relative to the tractor, and therewith the working depth, is controlled.

The device according to the preamble of claim 1 differs from conventional disc harrows wherein the discs are jointly fixed to one continuous shaft in that each disc is arranged on the end of a separate, pivotable standing shaft. This has the great advantage that the angle between the rotating shaft of the discs and the direction of movement of the tractor (the setting angle) can be varied without a continuous shaft having to be swivelled for this purpose through the desired setting angle. Thus prevented is that the discs on one of the outer ends of the harrow are moved far behind the tractor and that their working depth can no longer be properly controlled by the lifting device. In the device according to the preamble of claim 1 the setting angle of the discs can be varied without the distance between the discs and the tractor changing, whereby, using the lifting device, a virtually constant working depth can be simply maintained.

The disc harrow known from the US Patent No. 3,675,725 has the great drawback, however, that the standing pivot shafts are placed on the convex side of the discs connected thereto. This results in the danger of earth thrown up by an adjacent disc collecting and clogging between the standing pivot shaft and the disc, whereby the discs can jam.

It should be noted that from the US patent No. 2.659.291, a disc harrow is known having a plurality of discs arranged in pairs on a tool bar, each disc being rotatably mounted on a bearing at the free end of an associated standing shaft, the convex sides of the discs of each pair facing each other, and the standing shafts being placed on the concave sides of their associated discs.

In the US Patent No. 2,768,864 a disc harrow is disclosed having a plurality of parallel discs that are rotatably mounted on lying spindles through bearings. The lying spindles are arranged at the free ends of obliquely extending, fixed shanks and are very short, in order to obtain a very compact construction.

The present invention has for its object to provide a ground working device of the type described in the preamble of claim 1, with which the above stated drawback does not occur. This is achieved according to the invention in that each pivotable standing shaft (4) is placed on the concave side of its associated disc-shaped body (6), and the length of the lying shaft (5) is such that the distance between the axis of the pivotable standing shaft (4) and said bearing is at least equal to or longer than the axial dimension of said bearing, and so preventing the clogging of earth between the disc-shaped body (6) and its associated pivotable standing shaft (4). Thus obtained is a reliable and robust disc harrow with separately pivotable discs which is suitable for use in a large number of ground types, without the risk of clogging.

In preference the convex side is smooth. This prevents earth possibly clogging on the convex side whereby bearings that may run through the disc-shaped bodies to the convex side could become jammed.

In order to prevent earth that may be carried onto the concave side of a disc being able to collect between the disc and its pivot shaft, whereby the disc could become jammed, the distance between each pivot shaft and its associated disc-shaped body increases in the direction from the rotational centre point of the body to its rim.

The soil working device can be further provided with means arranged at the rear of the frame for attaching a height-adjustable cultivator. Because the cultivator tends to dig itself into the ground the working depth of the discs is kept constant to an even greater extent.

Mentioned and other features of the device according to the invention will be elucidated on the basis of an embodiment, wherein reference is made to the annexed drawing in which corresponding reference numerals designate corresponding components, and wherein:

• fig. 1 shows a perspective view of a first embodiment of the device according to the invention;
• fig. 2 is a partially sectional view of a detail of the setting means of the device; and
• fig. 3 is a side view of a device according to the invention having attached thereto a cultivator and a second device according to the invention.

A ground working device 1 (fig. 1) normally designated as disc harrow comprises a frame 2 in divided form whereon at regular mutual intervals between both parts bearing means 3 are suspended by means of gripping members 23. Pivotally mounted in the bearing means 3 are the first outer ends of standing shafts 4. The free ends of the standing shafts 4 are provided with lying shafts 5 on which disc-shaped bodies 6 are rotatably mounted. The standing shafts 4 are arranged on the concave side of each disc-shaped body 6 so that earth thrown up by an adjacent disc-shaped body 6 cannot collect and clog between the standing shafts 4 and the disc-shaped body 6. Jamming of the disc-shaped body 6 is thus prevented.

For adapting of the setting angle of the disc-shaped bodies 6 the disc harrow 1 is provided with setting means 24.

Because the disc-shaped bodies 6 are each pivotable relative to the frame 2 the latter does not have to swivel relative to the direction of movement of the tractor 15. The distance D between the rear wheels of tractor 15 and the device 1 can thereby be minimal and owing to the short-moment arm the working depth of the disc-shaped bodies 6 can be well controlled by the lifting device of an agricultural tractor 15.

Fixed to each standing shaft 4 is a first extremity of a radially extending adjusting body 7 (fig. 2). The other extremity of the body 7 is provided with a hole which co-acts with an opening 9 arranged in an adjusting member 8 with detachable pin-like fixation means 10 to attach the adjusting body 7 pivotally to the adjusting member 8. The outer end of the adjusting member 8 is likewise provided with a number of openings 11 which co-act with an opening arranged in a connecting member 12 joining both frame parts 2,3 and second detachable pin-like fixation means 13 to fix the adjusting member 8 in a determined position relative to the frame 2.

The disc harrow 1 further comprises a frame 14 with which the harrow 1 is attached to a three-point lifting device arranged on the rear of tractor 15. In order to prevent the occurrence of transverse forces and moments around a vertically extending top axis of the tractor 15 the harrow 1 in the embodiment shown here is of symmetrical construction relative to the centre line of the tractor 15.

To change the setting angle of the disc-shaped bodies 6 the disc harrow 1 is raised by the lifting device so far that the disc-shaped bodies 6 are free of the ground, whereafter the pin-like fixation means 13 connecting an opening 11 and an opening in the connecting member 12 is released, the adjusting member 8 is moved such that the disc-shaped bodies 6 are pivoted by the adjusting bodies 7 in the desired direction and the disc-shaped bodies 6 are fixed in their new position by placing the releasable pin-like fixation means 13 through one of the other openings 11 and the opening in the connecting member 12.

Although not shown in the drawings, the shape of the standing shaft 4 may be is adapted to the curvature of the disc-shaped body 6 such that the distance between the standing shaft 4 and the disc-shaped body 6 increases in the direction from the centre point of the body to its rim. Embodying the standing shaft 4 and the disc-shaped body 6 diverging in this manner prevents any earth adhering to the concave side of the body 6 from collecting at the location of the standing shaft 4, whereby the disc-shaped body 6 would still become jammed.

The setting angle is selected like the angle of inclination in accordance with the type of ground, the sort of cultivated crop and/or type of weed. In the embodiment shown, the disc-shaped body 6 is arranged about a bearing 30 which extends on the convex side of the disc-shaped body.

It is however also possible for the bearing 30 to be placed against the disc-shaped body 6 on the concave side, so that the convex side of the body remains substantially smooth. There is then no danger whatever that the action of the bearing 30 can be affected by the thrown-up earth.

It may be desired to vary the distance in transverse direction between the various disc-shaped bodies 6. To this end the bearing means 3 in which each standing shaft 4 is mounted can be releasably arranged on the frame (fig. 1). The bearing means 3 can then be displaced in transverse direction and fixed in particular desired positions by means of pin-hole connections 16-18.

By attaching a cultivator 19 to the frame 14 of the first disc harrow 1 in the manner shown in fig. 3 the working depth of the disc-shaped bodies 6 can be precisely controlled. The position of the cultivator 19 relative to the disc harrow 1 is controlled using (for instance hydraulic) adjusting means 20. When the harrow 1 is lowered by the lifting device fixed to tractor 15 the teeth 21 of the cultivator will dig themselves in and, depending on the position of the adjusting means 20, pull the disc-shaped bodies 6 of the device 1 to a greater or lesser degree into the ground. Thus obtained is a virtually constant working depth.

The embodiment of the device 1 shown here comprises a second device 22 according to the invention fixed to the elongation of connecting members 12, 12. The addition of a second disc harrow 22 is of importance if the first harrow 1 is provided with disc-shaped bodies 6 which are all positioned in the same direction and which is thus asymmetrical. Use of a single disc harrow 1 results namely in such a case in the occurrence of transverse forces and moments making the tractor 15 difficult to control.