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                 Harvesters are automated wood harvesting machines that have been used since the
                 beginning of the 1980s for the felling and preparing of trees without heavy manual
                 labour. The so-called harvester head, at the front of the machine's boom, is responsible
                 for marking, gripping and felling the trees. These are then fully automatically delimbed,
                 debarked and cut to length for removal in accordance with the specifications.

               An automated  wood harvesting machine  is usually  used in
               rough terrain, far away from modern civilization. It is exposed
               to extreme weather conditions in the forests and is designed
               for temperatures ranging from very warm to extremely cold.
               The wood harvesting  head  on  the boom  of the machine is
               very exposed and therefore constructed  extremely solid.
               Nevertheless, it must be possible to control the many moving
               components with high precision and reliability.
               The dimensions and execution of the harvester head and the
               hydraulic components  used in it are largely  determined by
               the size of the trunk and the type of wood to be harvested.
               The hydraulic system is used to control the feed rolls or feed
               rollers, the measuring devices, the chain saw drive including
               chain tensioner, the chain lubrication, the sword feed as well
               as the delimbing knives and the colour marking unit. Thanks
               to  high  precision,  robustness  and  reliability,  proportional  or
               mechanically adjustable pressure  reducing  valves  and  flow
               control valves from Wandfluh have been used for many years
               for this demanding work.

               On a harvester, common standard valves are used, such as the
               MVPPU10 pressure relief valve to control the feed roll and the
               delimbing knife, or the BDIPM22 pressure reducing valve to
               control the saw-bar. On the other hand, numerous customer-
               specific special valves are adapted to the respective harvester
               head, for example for pilot control.

               •  Pressure relief valves with fast response time and low hysteresis
               •  Pressure reducing valve with fast response time for pressure build-up and unloading
               •  Valves with high contamination and water resistance
               •  Special solenoid coils for use in warm climatic conditions

               WANDFLUH MOBILE       |          APPLICATION       |          HARVESTER         |          PAGE 5
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