Folding power harrows, thanks to their modern solutions that provide great versatility, can create an excellent seed bed on both ploughed and hard ground
Pier Luigi Scevola
Power harrows are very versatile tools: they can create an optimal seedbed from ploughed, coarsely tilled or even hard soil. The creation of an optimal seed bed is essential to ensure seed germination, deepening of roots, harmonious development of cultivated plants and therefore abundant and profitable harvests. In particular, folding power harrows are a very effective solution for modern farms seeking high productivity. Despite their considerable working width, foldable rotary harrows can be easily transported thanks to their hydraulic folding, which considerably reduces the transverse dimensions and thus allows easy transport even on public roads. Below are the typical features of modern foldable power harrows.
Hitch and folding frame
Folding power harrows are equipped with a robust hitch that allows attachment to the three points of the tractor’s rear lift. This hitch can be equipped with fixed or pivoting systems for attachment to the lower lift parallels. Since folding rotary harrows have considerable working widths (even up to 6 metres), the adoption of pivoting systems for attachment to the lower parallel bars of the lift is a suitable solution for better adaptation of the implement to the ground profile. In fact, the two halves (half-frames) that typically make up folding power harrows must adapt to ground conditions and must be able to oscillate, even by 2 or 3 degrees, to better conform to the ground profile. The attachment hitch of power harrows is attached to the two half-frames that make up the harrow and which are folded by the action of robust hydraulic cylinders powered by the tractor’s hydraulic circuit. The action of these hydraulic cylinders reduces the transversal dimensions of the folding rotary harrow to within three metres, or at least within the limits of the tractor’s profile, thus allowing easy transfers, even on public roads.
Tanks, gears and transmission of movement to the tines
The folding power harrows consist of two half-frames made of very sturdy steel profiles that incorporate the two tanks containing the pinions to which the tine troughs are attached. These tanks are made of very thick steel (typically 6-8 mm) to resist torsional stress and ensure a long life. In addition, the tanks also have a considerable depth since they must accommodate the gears that govern over the movement of the teeth, as well as the lubricating oil that also has the task of removing the heat generated by the friction of the movement.
The teeth of the folding power harrows have rotational movement on the vertical axis, transmitted from the tractor’s PTO through a cardan shaft to a transfer box typically of 1000 rpm which transfers the movement, by means of rotating axles or cardans, to two gear boxes placed in the middle of each tank. In turn, through pinions, rotating axles and bevel gears, these gearboxes transmit the movement to the toothed crowns contained in the tank, toothed crowns to which the tooth carriers are connected. The optimal configuration has four tine carriers per meter working width. In fact, this arrangement allows the use of gears with a small diameter, which also involves a slim harrow design and a short attachment; the leverage effect on the tractor is reduced, resulting in less lifting effort and greater stability of the work site consisting of tractor and folding power harrow.
There is no shortage of innovative elements in the layout of the hitch and the transfer box: the transfer box of the Maschio Gaspardo Jumbo Isotronic folding rotary harrow, for example, uses an oil recirculation system that, driven by a gear pump, uses the oil contained in a tank inside the third point hitch. In this way, in addition to reducing operating temperatures, it is possible to achieve less degradation of the oil properties, an increase in the time interval for oil replacement, a lower risk of machine downtime and greater productivity.
Suitable tines even on hard soil
The tines of the folding power harrows are inserted two by two on the tine carriers and have a shape that allows easy penetration deep into the soil; they break up the clods with great ease, refining the soil quickly, so that the seedbed is soft and without processing soles. The result of the work of the tines allows the roots of the plants to develop in the soil easily and orient themselves in search of water and nutrients, firmly anchoring the plant to the soil. Among other things, in order to effectively work the hard soil, the tines take on a curved shape at their lower ends, which gives their action even greater incisiveness and facilitates the incorporation of crop residues into the soil. Typically the tines have a length between 290-330 mm so that they can work without problems at a depth of even 20 cm without excessive wear of the components or excessive fuel consumption. In addition, the teeth are equipped with a quick release system to facilitate their replacement and maintenance of the harrow. In this regard, a particular fixing method requires that the tooth is secured to the support by means of a clip and locked in its seat thanks to a cotter pin. This solution allows a very quick tooth replacement, without the need for tools or even the dismantling of the entire tooth-holding structure.
Rear rollers also with hydraulically adjustable
The control of the working depth of the folding power harrows is entrusted to sturdy rear rollers that also perform the functions of equalizing and reconsolidating the worked soil. Among the most used are cage rollers, ideal for virtually any terrain except sandy soils. Other rollers that are widely used in modern folding power harrows are packer rollers, steel and rubber coated spirals and rollers with ribs or rubber wheels. Usually the adjustment of the rollers takes place mechanically through continuous screw systems or with the interposition of steel pins on perforated rods or rubber dowels on shaped steel axes. Lately hydraulic systems have also appeared equipped with sturdy hydraulic cylinders powered by the hydraulic circuit of the tractor which allow the position of the rear brake rollers to be adjusted while remaining comfortably seated in the cab.
