Hooks and tow eyes: some possible combinations of comfort and safety

One of the new features introduced by Mother Regulation includes the possibility of using coupling systems between tractors and equipment, i.e., hooks and tow eyes. Previously not allowed in Italy, these systems can instead make operators' work even safer and more comfortable

We have repeatedly emphasized how important Mother Regulation has been to farmers for introducing impactful innovations for road travel and safety while working. To optimize farmers' working time and costs, which has fostered the construction of the latest generation of machinery - faster, larger (considering the length of the agricultural train) and with greater towing and loading capacities - the Mother Regulation has introduced additional construction requirements that have transformed the machines and made their components more performing: it is enough to mention axles, suspensions, braking systems. Manufacturers have invested heavily in these systems in order to ensure high standards of safety and driving ergonomics. Among the crucial components designers have had to work on over the past few years, there are definitely the coupling devices between the agricultural tractor and the towed vehicle: we are talking about the tow hitch installed on the tractor and the tow eye fitted to the towed machine. First and foremost, the current legislation requires these two parts to be subjected to more severe rupture tests than the previous test protocols, flanking static tests with dynamic ones:  the expectation of vehicles on which they are installed having a speed above 40 km/h was instrumental in updating the test trials. The other major novelty introduced by the Mother Regulation was to allow also on the Italian market the installation, on tractors and towed equipment, of hooks and tow eyes that are allowed and used in other European countries: As a matter of fact, under the previous legislation, only the 'homegrown' CUNA hitch could be installed on the 'Italian market' tractor and specularly the CUNA type eye on towed equipment. It represents a real 'revolution' because, for several years, farmers had complained about this purely legislative 'rigidity' that did not allow them to enjoy the advantages of other possible combinations of hooks and eyes. As a matter of fact, each type of hitch, combined with its respective towing eye, can offer more or less advantages in terms of driving comfort, wear and tear on the assembly, driveability, vertical load that can be unloaded on the hitch, ease of hitching, and permitted articulation during maneuvering. Below, in detail, the new types of hook-eye combinations which are finally allowed in Italy. The list of installable hooks includes, in addition to the already mentioned CUNA (strictly defined by technicians as a 'fixed pin' hook and complying with the ISO 6489 Part 5 standard), the 'swivel pin' hook, typical of the German market and complying with the ISO 6489-2 standard; the 'hook 'hook,' very popular in the Anglo-Saxon market and complying with the ISO 6489-1 standard; the 'Piton' hook, typical of the French market and complying with the ISO 6489-4 standard; the 'ball' hook, typical of the northern and eastern European markets (Germany, Poland in the lead) complying with the ISO 24347 standard; the tow bar complying with the ISO 6489-3 standard, having different dimensions than the CUNA tow bar typical of the Italian market and complying with the ISO 6489-5 standard. Hence, the industry of the sector makes available a variety of mechanical devices; however, it is important that the user correctly matches the hook with the respective eye. In fact, the coupling mechanics between hooks and rings follow precise criteria at the design level to allow for the correct degrees of freedom. This is because the shape of the hook is designed to allow the corresponding eye certain minimum angular rotations in the horizontal plane, in the vertical plane and around the longitudinal axis. An incorrect coupling of hook and rings can lead to serious consequences for the operation of the agricultural train, such as the breakage of one of the two components and the consequent detachment of the towed vehicle from the tractor or the overturning of both convoys of the agricultural train. Legislative and regulatory references exist (Delegated Act No. 208/2015 to Reg. 167/2013 and ISO 22471 standard) that discipline the correct coupling of coupling devices:  the related pairing table is also shown in the registration documents of agricultural vehicles and the operation and maintenance manuals so that farmers can make use of this essential information at any time. To complete the picture of the possible combinations of hooks and towing eyes currently allowed, it is necessary to mention another possible combination referred to in the Ministry of Transport Circular Prot.  134 of 4.01.2018: in fact, the circular reports the possibility of also being able to combine tractors equipped with a towing bar cat. 4 complying with ISO 6489-3 with towed vehicles equipped with Z-type swivel eye complying with ISO 5692-3 (or equally CUNA NC 438.06 cat. F3).   However, this is a possibility provided only in the Italian market. This is exactly why FederUnacoma has requested the revision of Delegated Act No.  208/2015 and the ISO 22471 standard, thus allowing this particular type of coupling as well to be counted among those allowed in Europe. FederUnacoma, in addition to the above combination, has also asked in the proposed amendment to the European legal provisions to be able to include another possible coupling that field tests and software have properly verified, namely that between the cat. z fixed pivot hitch conforming to ISO 6489-5 and the eye referred to in ISO 21244.

Then, in the area of coupling devices between tractors and towed vehicles, the Mother Regulation introduced another major innovation, which farmers have also desired for many years: the new tractor-vehicle connection towed through linkage arms. This connection, which has been widespread abroad for many years but which in Italy is not yet provided for in the Highway Code, makes it possible to achieve greater steering angles than the traditional hook-eye connection, which is useful, for example, for steering at the end of rows in narrow spaces. Compared to the conventional and existing linkage between tractor and semi-carried equipment, the peculiarity of this new linkage system lies in the presence of a central joint that allows the towed machine to steer around bends. Instead, in the case of semi-supported equipment, the pivoting wheel allows the equipment to steering around bends.