Abstract: A piezoelectric actuator unit 10 for valve switching has a piezoelectric element changing its size on the application of a control voltage for switching the valve. So as to ensure a Totmann (safety) function of the valve and a fast return of the piezoelectric element into its initial position, the piezoelectric actuator unit 10 comprises a discharge circuit with at least one discharge element 21, 31 connected to the piezoelectric element 11. Discharge of the piezoelectric element is effected when the actuator is in its initial, safe position. The discharge circuit has to be switched actively so as to be able to exert a maximum stroke with the piezoelectric actuator.

Abstract: The invention relates to a mining electromagnet for the switching of hydraulic pilot valves or main control valves used in underground mining operations, with a coil which can be connected to an intrinsically-safe power unit, with an armature which can be displaced by application of current to the coil and with an electronic control device 20, by means of which the current which is conducted to the coil can be set during the drawing-in phase of the armature to an excitation current, and in its holding phase can be set to a holding current which is lower than the excitation current.

Abstract: Longwall face equipment for use in extraction in underground mining, comprising electrohydraulically operated support units each having a support controller 6, with at least one power unit being provided that supplies at least two support controllers 6 of differing support units with power, and with a bi-directional coupler being connected between the power unit and the at least two support controllers 6 and providing galvanic isolation between the power unit and the support controllers 6 and/or groups I, II of support controllers 6. The couplers permit communication between the two support controllers 6 and/or groups I, II of support controllers. In order to simplify the arrangement of the face, the coupler 12 is integrated into the power unit 11 or is flanged directly onto the housing of the power unit.

Abstract: A method and a circuit arrangement (10) for the measurement of earth leakage in intrinsically safe current feeds to electronic control units (4) for underground mining installations and machines, whereby at least one earthed control unit is connected to the two intrinsically safe potentials of an intrinsically safe direct current supply (1) and at least one earth leakage sensor (20) is provided for earth leakage measurement with which steps of the periodical application of a test potential (Umess) from an intrinsically safe switchable test voltage source (21) to an RC-element (22), isolated from earth (8) by means of decoupling capacitors (C1, C2), measurement of the charging or discharging current behaviour of the RC-element (22) after each switching of the test voltage source (21) and comparison of the measured charging or discharging behaviour with stored reference data.

Abstract: A controller is disclosed for control operations in underground mining, especially for controllers to control support shields. The controller utilizes a central unit with a microprocessor and assigned, programmable memory devices for the storage and processing of software as well as a connector unit with connectors or circuits for communication between the controller and other controllers and/or actuators, sensors or the like, that are to be controlled with the controller. Both the central unit and the connector unit utilize a modular design. A collection of modules with different performances and/or functionalities are provided for both the central unit and the connector unit to form the hardware of a controller. The modules can be combined with one another and coupled together according to a modular concept.

Abstract: An electro-hydraulic assembly for use in underground mining is disclosed. The assembly includes a hydraulic component, such as a valve block for an underground self-advancing roof support, as well as actuators and/or sensors which have a housing and can be connected or are connected via a data-transmission system to a control unit. A function (e.g. withdrawing the support, setting, advancing, or the like) can be activated at the hydraulic component by each actuator, and/or a hydraulic state associated with a measuring point of the hydraulic component or another measured variable associated with the self-advancing roof support can be measured by each sensor. A reader unit is associated with each actuator and/or sensor in its respective housing, and an information element or transponder is associated with the hydraulic component for each function, each control valve, or each measuring point.

Abstract: A solenoid operated hydraulic valve for electro-hydraulic controlled underground mining installations such as advancing support frame controllers, with an actuator housing holding coil bodies, an armature, a magnetizable core, and an operating pin of at least two solenoids. The head end for the operating pins of each solenoid has a cut-out for an operating stroke adjuster. A head plate removable from the actuator housing is provided with a manual operating device for each operating pin and is fastened to the head end of the actuator housing with a head seal between them, a removable valve block accepting the hydraulic multi-way valves and an interposed base seal fastened to the actuator housing base. A housing having a socket connects to an intrinsically safe current supply and accepts the operating electronics for the solenoids, and is located on the side of the actuator housing. In each head end cut-out, an electronic protective circuit for the associated coil body is arranged.

Abstract: The warning tone transmitter (10) according to the invention has a piezoelectric horn element (12) with two input connectors (29, 30) for the application of the supply voltage at a determined frequency and has a circuit arrangement (14) fed from the current supply, which generates the supply voltage. In order to be able to receive confirmation that the horn signal is actually generated by the warning tone transmitter (10) and in order to be able more easily to calibrate the warning tone transmitter (10) such that it is driven at its resonant frequency the piezoelectric horn element (12) has an additional output connector (34), which, when the horn element (12) is fed with the supply voltage, generates an answering signal taken to the circuit arrangement (14) if the piezoelement is actually oscillating. The magnitude of the answering signal is a value for the sound volume of the warning tone transmitter (10).

Abstract: The pressure cell device according to the invention serves for measuring hydraulic pressures in hydraulic mining devices in an inherently secure service region. It is provided with a connection element which can be connected to a pressure reception connection and with a sensor housing, on the inside of which is arranged a hydroelectric pressure transducer which is pressurised by the hydraulic pressure present at the pressure reception connection and converts this into an electrical signal. So as to ensure high measurement accuracy over a long operating period, without it being necessary to have exchanges of the pressure transducer or its new calibration, it is provided according to the invention that the pressure transducer comprises a ceramic pressure measuring cell.

Abstract: The present invention relates to an electrohydraulic control system (10) for an underground support system, with a valve block (1) which accepts grouped electrically-operated actuators for example electro-magnets (2, 2′) and several control valves of hydraulic valves switched with these electro-magnets and with a circuit board (7) containing an electronic circuit to which all the actuators (2, 2′) of the valve block (1) are connected through a disconnectable plug-in connection. The circuit board (7) is connected via a cable (21) to a controller (20) for data communication in the support system. The invention allows simultaneous connection of all the electro-magnets (2,2′) with the circuit board (7). For this purpose the circuit board (7) is located in a hood-type enclosure part (9) which is attachable to the back (3) of the valve block (1) and when assembled forms a sheet over all the electro-magnets (2,2′).

Abstract: The present invention relates to a method for operation of an electro-magnet (2, 3) connected to an intrinsically safe direct current circuit which can be switched under control between two positions for the operation of the closing body of a hydraulic valve (5, 6), whereby using of an electronic control unit, the coil windings of the electro-magnet (2, 3) are taken in the pull-in phase of the armature of the electro-magnet to an exciting current and in the retaining phase of the armature to a lower retaining current as opposed to the excitating current, and a device with which the retaining current reduction is realised. In accordance with the present invention it is proposed that the actual current in the coil winding following the actuation of the electro-magnet (2, 3) is continuously measured and evaluated to detect the movement of the armature.

Abstract: A solenoid operated hydraulic valve for electro-hydraulic controlled underground mining installations such as advancing support frame controllers, with an actuator housing holding coil bodies, an armature, a magnetizable core, and an operating pin of at least two solenoids. The head end for the operating pins of each solenoid has a cut-out for an operating stroke adjuster. A head plate removable from the actuator housing is provided with a manual operating device for each operating pin and is fastened to the head end of the actuator housing with a head seal between them, a removable valve block accepting the hydraulic multi-way valves and an interposed base seal fastened to the actuator housing base. A housing having a socket connects to an intrinsically safe current supply and accepts the operating electronics for the solenoids, and is located on the side of the actuator housing. In each head end cut-out, an electronic protective circuit for the associated coil body is arranged.

Abstract: The present invention relates to a method and to a circuit arrangement (10) for the measurement of earth leakage in the current feeds in the intrinsically safe current supply (1) to the electronic control units (4) for underground mining installations and machines, whereby at least one earthed control unit is connected to the two intrinsically safe potentials of an intrinsically safe direct current supply (1) and at least one earth leakage sensor (20) is provided for earth leakage measurement with which steps of the periodical application of a test potential (Umess) from an intrinsically safe switchable test voltage source (21) to an RC-element (22), isolated from earth (8) by means of decoupling capacitors (C1, C2), measurement of the charging or discharging current behaviour of the RC-element (22) after each switching of the test voltage source (21) and comparison of the measured charging or discharging behaviour with stored reference data are made by means of a microprocessor (24) using stored reference da

Abstract: The warning tone transmitter (10) according to the invention has a piezoelectric horn element (12) with two input connectors (29, 30) for the application of the supply voltage at a determined frequency and has a circuit arrangement (14) fed from the current supply, which generates the supply voltage. In order to be able to receive confirmation that the horn signal is actually generated by the warning tone transmitter (10) and in order to be able more easily to calibrate the warning tone transmitter (10) such that it is driven at its resonant frequency the piezoelectric horn element (12) has an additional output connector (34), which, when the horn element (12) is fed with the supply voltage, generates an answering signal taken to the circuit arrangement (14) if the piezoelement is actually oscillating. The magnitude of the answering signal is a value for the sound volume of the warning tone transmitter (10).

Abstract: A method for controlling the main and auxiliary drives of conveyors, for example, in underground mining. The drives are controlled as a function of the loading of the conveyor in such a way that in a low load range of the conveyor the auxiliary drive produces a higher output (20.sub.I) than the main drives and as the load increases the output advantage of the auxiliary drive in relation to the main drives is reduced. This special load distribution to auxiliary and main drives has the advantage that sagging of the conveyor element, for example the chain of a scraper chain conveyor in the inaccessible and concealed lower strand, close to the main drive, can be prevented. The risk of damage to the machine frame or conveyor chain is thereby reduced.

Abstract: A method for determining the active power (P) of asynchronous electric motors of winning and conveying equipment in underground mining. According to the invention, particularly easy and accurate determination of the instantaneous active power of the motors is obtained by storing the individual motor characteristic (P(n); M(n)) of each motor in a computer, by detecting the instantaneous speed (n, n') of the motor with the aid of a tachometer and by comparing this speed with the characteristic stored in the computer, the active power being derived from the torque value or power value assigned to the detected instantaneous speed, as stored in the computer. This particularly rapid and simple calculation of the power value does not require any readings to be taken at the power supply to the motors.

Abstract: The invention employs pressure and displacement sensors for the automatic monitoring and adjustment of the pre-tension of endless belts, in the form of chains or the like, which sensors determine the pressure in the cylinder space and the movement of the piston of the tensioning cylinder, and the measuring signals from which sensors are evaluated by an electronic evaluation and actuation unit. In this respect the evaluation and actuation unit calculates from the measuring signals the changes in pressure which occur over a predetermined partial stroke of the piston of the tensioning cylinder, wherein these changes in pressure reflect the state of tension of the chain belt. When the chain tension is incorrect, the evaluation and actuation unit can therefore control the tensioning cylinder so that the optimum chain tension is set automatically.

Abstract: A drive system for driving a flexible elongate member such as a haulage chain for a mineral mining machine or scraper-chain assembly of a scraper-chain conveyor of a mineral mining installation employs main and auxiliary drive units each equipped with an electric asynchronous motor drivably connected through a gearing assembly to a sprocket around which the chain or scraper-chain assembly is entrained. The gearing assemblies each employ a multi-disc clutch which is subjected to variable loading pressure and slippage by means of a valve actuated by electrical signals provided by an electronic controller. Each clutch acts through gears on a ring gear of planetary gearing and the ring gear wheel is subjected to a controlled supportive torque. The electronic controller is designed to actuate the associated valves to adjust the clutches to balance loading on the motors of the units.