Flexible tine harrow for the preparation of seed beds

It has long been known that a careful preparation of the field is essential to the conditions of growth of various crops and consequently to the obtainable yield and, therefore, a final harrowing and smoothing of the soil surface is frequently effected immediately before seeding for which purpose special flexible tine harrows and so-called rotacrats (crumbler drums) have been developed which should leave the soil surface as smooth as possible and without bigger clods. In this respect it is important that only a superficial layer of suitable depth is being worked by the harrow tines, and not less important is that the depth of processing is as constant as possible so as to obtain also an accurate sowing depth by the following mechanical sowing.

The purpose of the present invention is to provide an implement which in the best way fulfils these conditions.

More particularly, the invention relates to a seed bed preparing flexible tine harrow of the type comprising a main frame to be coupled to a tractor and in which a plurality of harrow sections are individually suspended, each harrow section comprising a set of harrow tines clamped in a tine frame which is adjustably suspended in an intermediate frame towingly connected with the main frame and having wheels or drums rolling on the soil surface.

Such harrows are known in which the intermediate frame solely by its own weight and the weight of the harrow tines and their frame rests on the wheels or drums which may be adjustable in relation to the intermediate frame, the towing connection from the main frame to the intermediate frame (and possibly also the suspension of the tine frame therein) being established by means of chains. Dependent on soil conditions such a seed bed harrow can yield a satisfactory working, but in several cases variations in the resistance to the harrow tines and in the bearing capacity of the soil surface will cause the tine frame to tilt or pitch which makes it impossible to filful the requirement of a constant harrowing depth.

As distinct from the prior embodiment it applies to the harrow according to the invention that each intermediate frame is connected with the main frame through a front link and a rear telescopic stay biased to extension, respectively, and that the link and the stay hinged to the intermediate frame are directed forwards/upwards and backwards/upwards, respectively, under such angles that their longitudinal directions intersect approximately in the level of the shares of the harrow tines.

During operation the intermediate frame suspended in this particular manner will be subjected both to a pull from the link and to a push from the stay. These pull and push forces may each be broken down in a horizontal, forwardly directed component and a vertical component directed upwardly and downwardly, respectively, and by an appropriate biasing of the telescopic stay it can be ensured that the vertical components neutralize each other when the force directions intersect in the said manner. The resulting force on the set of harrow tines will then become parallel to the soil surface and will be effective mainly in the same plane as the resistance that the shares of the harrow tines must overcome and, consequently, variations in this resistance will not result in a moment of force capable of provoking a tilting or pitching movement as mentioned above.

An embodiment of the flexible tine harrow according to the invention is illustrated on the drawings in a strongly simplified side elevation.

The illustrated harrow comprises a main frame 1 which through a pull rod or hitch 2 can be coupled to a tractor and which at its rearmost end is provided with a transport wheel 3, illustrated in its raised, inoperative position. The implement may as well be adapted to be suspended on the tractor so that the transport wheel becomes superfluous, and the main frame 1 may in an ordinary manner be composed of a centre section and a pair of side or wing sections which may be folded over the main section when the implement is to be transported on public roads.

A number of individual harrow sections 4, e.g. seven, of which only one is seen in the drawing, are suspended side-by-side in the main frame 1. Each of said sections comprises a set of harrow tines 5 clamped in a tine frame 6, which through a pair of ordinary height adjusting mechanisms 7 with handles or levers 8 is suspended in an intermediate frame 9. Both in front of and behind the harrow section 4 said intermediate frame is provided with one or more drums, for instance so-called crumblers or rotacrats 10 which determine the height of the intermediate frame 9 above the soil surface 11. Said height too may be adjustable.

To transmit the pull force from the main frame 1 to the intermediate frame 9 and thus to the harrow section 4 there are provided, on the one hand, a link connection 13 at the front end of the intermediate frame and, on the other hand, a telescopic stay 14 above the harrow section 4. The link or lever 13 of the link connection is hinged to a mounting plate 15 on the main frame 1 and to the intermediate frame 9, its hinge point 16 on the mounting 15 being positioned ahead of its hinge point 10 on the intermediate frame 9. The stay 14 may appropriately be constituted by a hydraulic cylinder biased to extension, which in a manner known per se is hydraulically connected with the corresponding cylinders associated with the other harrow sections and the upper end of which is supported by a mounting plate 17 from which the stay is directed forwards/downwards to a mounting fitting 18 on the intermediate frame 9.

As illustrated in dotted lines, the longitudinal directions of the link 13 and the stay 14 intersect in a point 19 which is on level with the shares of the harrow tines 5, and the pull and push forces transmitted through the link and the stay may, therefore, as explained above, be combined into a horizontal resultant in the intersection point 19.

The hydraulic series connection of the cylinders of the stays 14 is intended, as is the case with analogous arrangements in prior harrows, to ensure uniform working depth of the harrow tines associated with the various intermediate frames even through the field is not plane transversely to the driving direction of the harrow.