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MDA Technologies 4/2015

MDA Technologies 4/2015

A valve for every

A valve for every scenario Ulrike Ballnath, Tobias Kohler, Korbinian Mayer Control functions in mobile work machines have to meet varying requirements, but one that is common to all is the need, in most cases, for several hydraulic consumers to be operated simultaneously. Hawe Hydraulik offers valves for almost every scenario. Authors: Ulrike Ballnath, Press Officer Tobias Kohler, Key Market Manager Korbinian Mayer, Key Market Manager All Three: Hawe Hydraulik SE, Munich Whether they’re used in cranes, lifting platforms, agricultural and forestry machinery, or mining machines – the ideal solution is to use proportional directional spool valves with a load sensing system, because these adapt the pressure and volume flow to the momentary requirements of one or more consumers. The machine operator can precisely adjust the direction of motion and the speed of the hydraulic consumers, with infinitely variable control. The load sensing system was first used back in the late 1970s in the proportional directional spool valves produced by Munichbased Hawe Hydraulik SE. Over the past decades, it has been continuously developed so that today it is possible to construct a custom hydraulic control unit with one valve type in several sizes. It is common practice to also equip the valve with a flow controller –so it becomes possible to perform several functions not only in parallel but also independent of the load. For low volume flows The hydraulic positioning and actuator functions that are essential in agricultural machines and municipal vehicles usually only require low rates of flow. What counts is the precision with which the functions are implemented. Flow rates of less than 40 l/ min are usually adequate, and Hawe Hydraulik has now developed the proportional directional spool valve type EDL for precisely this purpose. The valve is controlled directly and actuated electrically. The flow rates for individual consumers can be controlled proportionally and limited if necessary: for example, for functions in combine harvesters, forage harvesters and root crop harvesters and/or street- and drain-cleaning vehicles. A maximum of 50 l/min per consumer is possible. Spool pistons in seven graduated sizes offer optimal resolution and allow the speed of hydraulic motors in particular to be cont- 40 MDA Technologies 4/2015

MEASUREMENT AND CONTROL POS-123-U rolled with great precision. Flow rate can be reduced to as low as 3 l/min. Designed for system pressures of up to 320 bar, the type EDL has a higher compressive strength than comparable products on the market. The flow resistance is 50 % lower than normal, so that the valve improves the energy efficiency of the hydraulic system. For high speeds If pressures over 320 bar are required for additional consumers, the EDL valve can be combined with the proportional directional spool valves type PSL. These are used when flow rates up to 400 l/min are required. They are of valve bank design and manifold mounting design and are appropriate for connection to fixed-displacement and variable-displacement pumps. Each valve segment is load-compensated, and segments of different sizes can be combined. This type of valve can be used, for example, to speed up loader or forwarder cranes in forestry work. Special spool pistons allow precise and jerk-free acceleration and braking of the loading crane. The Hawe hydrau- 01 A valve bank consisting of proportional directional spool valves and directional seated valves for all types of functions in a loader wagon For every function there is a matching valve, all valves can be combined with one another lics specialists collaborate closely with their customers to determine what counter-pressure is needed. The valves are equipped with a spool piston that is matched to the cylinder conditions of the application and contains a precisely defined fine-control range that makes it as easy and straightforward as possible for the driver to move tree trunks. The product construction kit contains numerous spool variants that manage different pressure conditions. For improved energy balance Spool pistons with a regenerative function for lowering the articulated arm and extending the telescopic system on forestry vehicles also help improve the vehicle’s energy balance. The oil from the piston rod side is also used for this purpose: Instead of circulating it back into the tank, it is fed directly to the piston side. The pump only needs to deliver an amount equivalent to the volume of the piston rod. The regenerative spool-valve piston reduces the volume flow requirement of the hydraulic consumers. As a result, the hydraulic system is not only energy-efficient, it is also better protected against an insufficient supply of oil. This makes proportional directional spool valves with regenerative spool pistons especially desirable for hydraulic systems with small pumps and large numbers of parallel functions. Many different functions can be implemented in mobile machines with modular systems like those manufactured by Hawe Hydraulik. An agricultural loader wagon, for example, has drive functions that are digital positioning control modern and inexpensive design with analogue signal interface suitable for all proportional valves with OBE best positioning due to optimized and practical control functions Start-Up-Assistant expandable with power output stage or SSI-interface Elektronik GmbH Gewerbering 31 D-41372 Niederkrüchten Telephone: +49 (0)2163 577355-0 Telefax: +49 (0)2163 577355-11 E-Mail: info@w-e-st.de Internet: www.w-e-st.de For 16 years your partner for dynamic drive solutions

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