Importance

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Abstract

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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First Claim