DRIVING IMPRESSION: Lemken gave an early sneak peek of its Thulit pressure harrow at SIMA before testing continued last summer. We managed to catch up with one of these machines to see how the novel hydraulic tine pressure system operates.
Looking to expand its mechanical weed control line beyond the former Steketee products, Lemken has developed the Thulit, the firm’s first pressure harrow. It will be built at the new Crop Care factory in Dintelood in the Netherlands. When developing the new harrow range, the engineers wanted to avoid using the familiar combination of springs and cables, like others do, to control the tine pressure across the peaks and troughs. Instead, it has come up with a completely new and unique system using hydraulic pressure to control the tines, and accumulators to maintain an even load on all of the tines. It is similar to the approach used on the firm’s drill for setting the coulter pressure. Each tine is connected to a piston via a metal rod. These pistons are housed in a valve block, which provides the required pressure. Positioned along the front of the harrow, each valve block houses five, 12 or 16 pistons and is connected to its neighbour creating a fully enclosed system. And because the valves are interconnected, the pressure is the same from one end to the other. If some of the tines are on top of a ridge, while others are working the sides or in the bottom, the excess pressure is absorbed by the accumulator. The hydraulic blocks are double sealed.
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