Abstract: A safety switching arrangement that outputs a switching signal a switch or safety-oriented interruption of a circuit to control disconnection of a power supply for a load. The safety switching arrangement includes at least one evaluation circuit which emits an unsafe drive signal for the switch at an output. The safety switching arrangement also includes a programmable logic unit supplied with the drive signal(s) at an input and connected to the switch to drive the switch with a safe drive signal. The programmable logic unit can test and monitor the correct function of the switch during operation. A safe non-floating first terminal of the switch is connected to a respective feedback input of the programmable logic unit to monitor the potential state of said terminal. The relevant potential state during error-free operation corresponds to the safe drive signal for the at least one switch.

Abstract: A safety switching arrangement is proposed for outputting a switching signal for at least one switch or the safety-oriented interruption of a circuit which can be used to control the disconnection of the power supply for a load. In at least one embodiment, the safety switching arrangement includes at least one evaluation circuit which emits a respective unsafe drive signal for the at least one switch at a respective output. The safety switching arrangement also includes a programmable logic unit which can be supplied with the drive signal(s) at a respective input and is connected to the at least one switch in order to drive the at least one switch with a safe drive signal. The programmable logic unit is in the form of a testing and monitoring device which can test and monitor the correct function of the respective switch during operation.

Abstract: In order to ensure safe and reliable time-delayed signal outputting with a simple redundant structure of a circuit arrangement, a common actuating element acts on two timers with associated A/D converters. In this case, the time delay which is predetermined by the actuating element and is relevant for the outputting of the switching signal is determined by forming the difference between a total resistance, detected by measurement, and a first resistance element, detected by measurement. This is followed by a comparison of the difference, which reflects second resistance elements that is determined by computation, with a second resistance element which is determined by measurement. The switching signal is then output with a time delay when there is a match between the second resistance element determined by measurement and that determined by computation.

Abstract: In order to ensure safe and reliable time-delayed signal outputting with a simple redundant structure of a circuit arrangement, a common actuating element acts on two timers with associated A/D converters. In this case, the time delay which is predetermined by the actuating element and is relevant for the outputting of the switching signal is determined by forming the difference between a total resistance, detected by measurement, and a first resistance element, detected by measurement. This is followed by a comparison of the difference, which reflects second resistance elements that is determined by computation, with a second resistance element which is determined by measurement. The switching signal is then output with a time delay when there is a match between the second resistance element determined by measurement and that determined by computation.

Abstract: A machine is disclosed which is for use in mining or tunnelling work and employs a beam or arm supporting cutting means and connected through a support structure to a turntable carried by a movable chassis. The turntable is adjustably rotatable about a vertical axis and one or more piston and cylinder units are provided to raise or lower the arm in relation to the support structure. This structure is itself adjustably pivotable in relation to the turntable about a further axis which is generally aligned with the horizontal forward position of the arm i.e. in the direction of advancement of the mining or tunnelling work. In addition part of the structure connected to the arm is also displaceable along this further axis so that the cutting means located at the free end of the arm can be adjusted in respect of a variety of directions. The cutting means is itself composed of cutter rollers driven to rotate about an axis extending laterally of the arm.