Modern Technological evolution of combined harvesters

 

Combine harvesters are working machines manufactured in their current configuration since the first half of the 20th century. They have their origin in the fixed point threshers. Its development has been uninterrupted, both mechanically and from the (more recent) mechatronic point of view. Current models are highly sophisticated, resulting in high workability and high-quality results.

In the early days of cultivating grain species, harvesting and threshing were handled separately: plants were cut in the field and grouped into sheaves, manually threshed, either with a stick or by trampling animals.

Following the development of mechanization, fixed-point threshers appeared on the market around the 1830s. They consisted of a beater, a concave, sieves, a fan, and a straw walker, driven by a belt drive moved by stationary steam or endothermic engines or, more recently, directly by farm tractors. The latter also allowed machinery to be moved from one farmhouse to another, a task carried out until then by animal traction.

In 1836 They built the first combined harvester in the United States. This machine was designed to cut plants in the field and separate the wheat from the chaff, although still imprecisely. This harvester had a cutting width of about five meters and was pulled by about twenty horses. However, the lack of a suitable transmission unit and the tendency of the harvested grain to deteriorate due to excess moisture limited its propagation.

In 1915, International Harvester of Canton, Illinois, USA, launched the first line of trailed combines equipped with an engine to drive the threshing system. Case and John Deere introduced the first tractor-pulled models a few years later. Demand for these machines grew in excess, particularly after World War I. However, the presence of combine harvesters in Italy remained confined to a few large grain farms until after the war. In 1942, a leading expert in agricultural mechanics even wrote about combine harvesters "...this category of equipment does not present real and concrete interest from the point of view of the possible widespread application in Italy."

Despite this pessimistic prediction, the spread of the combine grew nationally after the end of World War II as the economy recovered. Major import brands include Massey Harris, McCormick, Claas, John Deere, and International Harvester. The first Italian model of a combine harvester was manufactured by Pietro Laverda de Breganze (VI) and presented at the Verona Fair in 1956. This model, named "M60", was equipped with a 35 Hp Fiat diesel engine; the mowing device was a 1.98 m wide single-body with the machine with a mechanical ratcheting lift fitted with an articulated reel and was provided, as a threshing apparatus, with an 8-bar beater and a concave that can also be adjusted while it works. The Laverda M60 was manufactured until 1963, with 974 units sold in Italy and Europe.

Threshing technologies:

The diffusion of this new machine brought about some problems related to the efficiency and the quality of the threshing. These were resolved by developing the two main categories by which combine harvesters are still commonly classified today: conventional, also known as "tangential flow", and axial flow.

A large footprint characterizes the former due to reciprocating straw walkers, adequate operating capacity, relatively low diesel consumption, and the ability to recover undamaged straw.

"Hybrid" combines:

The latter, however, are characterized by a more significant work capacity to process a high input biomass flow. They have a smaller footprint but do not provide for the reuse of the straw as, due to more vigorous action, the straw is excessively crushed before being released into the ground. An attractive solution, which falls between the two mentioned above, is that of the so-called "hybrid" combines. A conventional thresher/counterthresher is followed by a separation apparatus usually made up of a pair of counter-rotating rotors, which process the crop in an axial pattern. Regardless of the threshing device installed, these machines were initially designed to be used on flat terrain since, especially for conventional models, it is necessary to ensure the best biomass distribution uniformity between the thresher and the concave and then on the walkers. If this were not the case, the grain losses would increase unacceptably due to the inevitable overload of the related work organs. Since Italy has a high percentage of hilly and hilly land cultivated with cereals, in the late 1960s, so-called "levelling" and later "self-levelling" models appeared, that is, equipped with hydraulic actuators on the individual wheels. These were designed to keep the machine body horizontal in the turntable and retractor gears, allowing the cleaning system to function correctly in all conditions.

Once again, Laverda was the progenitor of production, with the M 100 AL model produced in 1971. These systems, which can be automatically adjusted via dedicated inclinometers, allow correct work on slopes of up to 25 per cent—uphill, 10 per cent downhill, and more than 35 per cent crosswise.

High mechanical complexity:

From a technological point of view, combined harvesters were immediately characterized by high mechanical complexity due to numerous moving parts and having to ensure their displacement simultaneously. To this day, several types of transmission allow the operation of the different components, with a certain preponderance of the hydraulic ones, which are more capable of making continuous and precise adjustments.

 Regarding the sensors, it is worth mentioning that it was precisely the combine harvesters that were among the first machines implemented for precision agriculture purposes, thanks to the installation of geolocalized production mapping systems, already described in an article previously. (see Machinery World no. 11/2021).

Detection and automation on board:

The most innovative features include 1. the position of the cutter bar: the header frame can be moved vertically, using hydraulic actuators, to define an optimal distance of the cutting unit from the ground surface. An exciting solution also consists of the possibility of making the cutter bar more flexible (thanks to its sectional conformation) and thus follow, more reliably, the profiles of even considerably irregular soils. This is very useful for threshing prostrate crops like soybeans, beans, peas, etc. 2. In the case of autumn/winter grain threshing, adjust the position of the reel according to the development and density of the biomass in the field. Precisely, a laser sensor controls the coil's depth and horizontal position according to the container's plant material. This results in even crop feeding, which improves threshing performance and optimizes engine power utilization; 3. Adjustment of the threshing equipment: it is possible to automatically adjust the distance between the beater and the concave (both in and out of the crop flow), the rotation speed of the beater, and the position of the gin bar, and the opening/ concave blinders closure. To constantly optimize machine performance, some specific solutions use data from a high-definition colour camera mounted on the head of the grain elevator. The resulting images identify distinct parts of the caryopsis, i.e., straw, glumes and glutes, and broken kernels. The resulting image processing can alert the operator if threshold values ​​are exceeded to improve culture cleanliness; 4. Who can modulate the fan's speed according to the slope of the land on which the machine works?

management functions:

Specifically, the speed automatically decreases when working uphill (to prevent excessive leakage from the rear of the combine). It increases instead when going downhill to avoid the clogging of the threshing unit. In addition to fan speed, some systems improve grain cleanliness by automatically managing the opening of the upper and lower sieves or by directly adjusting the forward momentum of the machine; 5. Distribution of waste in the field: Through 2D radar, it is possible to obtain an accurate image of the distribution profile of the waste particles ejected from the machine by detecting the position and speed of the airborne waste before it falls to the ground so that What can obtain an actual distribution profile. This results in uniform residue coverage behind the combine without specific operator intervention.

The diffusion of modern combined harvesters and continuous technological improvement makes them the absolute protagonists of modern agriculture.

The latest sales data also confirm this belief: in the 2020/21 season, the sale of these machines in Italy increased by around 30 per cent, from 290 units the year before to 376 in the most recent collection campaign.

Specifically, axial harvesters accounted for 37 per cent of the total, conventional 35 per cent and self-levelling 28 per cent, the latter figure testifying to the importance of mountain and mountain agriculture in the Italian reality.