28 December 2013, 00:00
Height and pressure controls for tractor mounted implements allow farmers effectively to work the soil and evenly distribute seeds, pesticides and fertilizers. As the conditions of the soil vary, the implements' various operating states must be controlled for optimal results. HAWE Hydraulik SE from Munich is showcasing the appropriate tractor controls at the Agritechnica.
Electro-proportional controls offer a whole range of possibilities of adjusting the contact pressure to the required implements. The controls enable the implement to be worked with a pre-defined weight or fully weightless. With an electro-proportional control the implement maintains the requested distance to the soil far more precisely than it would with such a mechanical relief as springs for example. Moreover, the pump needs to supply merely the volume flow required for the control sequence, which in turn saves fuel.
The floating position can be used in a completely open version. In this case, the two cylinder ports connect to the oil tank and external forces move the piston rod up and down. Integrating actuated over-center valves makes it possible to realize also a proportionally dampened system. The valve outlets are leakage-free when not actuated, avoiding a creeping lowering of the implements. HAWE Hydraulik uses as basic valve its proportional directional spool valves, type PSL, that come with a patented actuation.
Simple actuation of the hoisting unit via plunger cylinders merely lifts the implement, while the unit’s dead weight lowers it. To actuate the lifting cylinder, HAWE Hydraulik developed the connection block, type HMPL. The block comes with system pressure relief valves and a pressure compensator for constant displacement pump systems. An integrated zero-leakage proportional directional seated valve executes lifting and lowering movements with minimum pressure losses. This guarantees speedy lowering without loads as with light hoisting units in forklifts for example.
An expert presentation at the VDMA Booth in Hall 1 will inform visitors about the various pressure controls HAWE Hydraulik implements. The lecture will focus on "Hoist controls for mobile work machines: multiple functions, including floating and pressure control functions." Date: Wednesday, November 13, 2013, 12.30 am