Hydac Fluidtechnik Gmbh

Alois Hoffmann

Peter Bruck

Markus Bill

Hermann Albert

Gerd Anton Thiry

Harald Bär

A valve, in particular, a proportional seat valve or gate valve, includes a valve housing () and at least three fluid connections () extending through the valve housing. A main piston () extends in the valve housing (). A pilot piston () for executing a pilot control () may be controlled by a current-carrying magnetic device (). During an open pilot control (), fluid from one () of the connectors (), controlled by the main piston (), reaches the connector (), controlled by the pilot piston (), by a cross-sectional narrowing () in the main piston (). The pilot control () and, as a result of the corresponding pressure drop, the main piston () achieves a control position, controlling both fluid connections () with regard to fluid amount.

Valve

A circuit arrangement includes a load sensing system (LS) with individual loads () arranged in series forming a series section, and in parallel forming a parallel section. A hydraulic supply circuit () includes a supply pump (P) and a runback () for fluid. The load sensing system (LS) determines the highest load pressure in the series section and the parallel section. The loads of the parallel section can be actuated independently from the pressure level of the loads of the series section due to the highest load pressure being transferred as a control pressure to a valve unit () such that, as long as the load pressure of the parallel section is higher than the load pressure of the series section, the valve unit restricts the runback () so that the pressure of the supply pump (P) matches or exceeds the pressure required in the parallel section. Sufficient fluid pressure for the load in the parallel section is ensured independently of the number of loads in the series section.

Circuit arrangement

The invention relates to a valve that comprises at least one pump connection ( ), one tank connection ( ) and one consumer connection ( ), and a valve piston ( ) that is displaced within the valve box ( ). Said valve piston separates the pump connection ( ) from the tank connection ( ) in at least one blocked position and interacts with an energy accumulator ( ). A fluid stream that flows between the consumer connection ( ) and the tank connection ( ) is controlled by means of a control device ( ). The control device ( ) is configured as a fluid stream control that is integrated in the valve piston ( ) and that allows, contrary to known valves which use a diaphragm construction, reduction, by a constant value, of the volume flow to the consumer in a load-independent manner, thereby allowing for a proportional load-independent control.

A control device for hydraulically operated hoisting mechanisms used to raise and lower loads includes an electrically controllable throttle valve connected to a return line of the hoisting mechanism, and a pressure scale with at least one blocking position and one control position. The pressure scale operates in conjunction with an unblocking mechanism. When in its normal position, the pressure scale blocks the return line. The pressure scale assumes its control position in lowering of a load as a result of triggering of the unblocking mechanism. In the event of failure of the throttle valve, the pressure scale may be moved to its blocking position by the unblocking mechanism. In the event of failure of the pressure scale, the throttle valve assumes its blocking position. The load retention function is performed by two series-connected closed hydraulic actuators which can be electrically controlled individually. Both a hydraulic redundancy and an electric redundancy of the load retention function are provided as a result, so that higher safety requirements are satisfied.

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Saarbrucken, Germany

Alois Hoffmann