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.