Rugged Over Rocks and Roots

Extreme working conditions

Disc harrows are used for preparing soil. The metal discs (or tines) frequently have to till soil under tough conditions – stones can deal sharp knocks. Soil is rarely homogeneous, and every single disc has to be protected and insulated with a swivel joint. The inclination of the discs means they also have to absorb lateral forces. The company Quivogne, in the French region of Haute-Saône, builds agricultural machinery with 150 employees and sells in forty countries – around 15,000 items of equipment annually, including umpteen disc harrows.

As an innovative business, Quivogne’s focus is on high-quality machines and improving quality. It can prove expensive if a machine that has been delivered to the other side of the world does not function as desired. And the Frenchmen do not want to jeopardise their good reputation. The disc harrows have to penetrate and breakdown compacted soil – in this case, over a span of about 12 metres. To do this, they need a couple of hundred rubber cords – four per disc, that is, per swivel joint. Each group of four is mounted between an internal shaft and an external bracket applying pre-stress (see image).

Software for durability

“If you understand the importance of rubber cords and you want to do more than cross your fingers and hope, then you come knocking at our door,” says Philippe Kirsch pleased. Even advance field trials do not guarantee a long service life. Some manufacturers perform field trials – nothing happens, the machines are delivered, but then the complaints come in anyway. “Poor material is often done for after one year – especially with really tough soil,” says Kirsch. Many companies resort to excessive pre-tensioning of the rubber cords to compensate for the characteristics of cheap rubber. But even top products achieve nothing if they have not been installed correctly or the design is unsuitable.

Service life is always curtailed by such mistakes. But where do manufacturers begin to analyse the stresses? How and what feeds into the calculation? This is precisely why Angst+Pfister is far more than your standard supplier of rubber, because as a responsible technical partner, it can provide customised support. Angst+Pfister calculates the service life of the swivel joints by applying finite element analysis. Software scrutinizes the stress the materials are placed under and the rubber is adapted accordingly. Selecting and developing suitable materials are among Angst+Pfister’s core competencies. The analysis is carried out at the in-house laboratory and production facilities in Turkey. Close collaboration between the Development and Production departments means Angst+Pfister can offer cutting-edge high-tech compounds to meet stringent requirements and specifications. Even highly specialised requirements and bespoke needs regarding quality, plasticity and properties of customers can be satisfied. Particular attention is paid to flow qualities and processability. Ultimately, the in-house advanced testing facilities provide the required quality.