FEATURE MACHINE BUILDING, FRAMEWORKS & SAFETY Designed to actuate reliably and


traceably, protecting drive components from overload damage, torque limiting clutches frommayr power


transmission are being built into tunnel boring machines used around the world


Going underground... O


ften described as ‘moving factories underground’, tunnel boring machines are


designed to withstand the harshest conditions. Often excavating tunnels through both soft and hard materials for hours on end, these need to be built using components of the highest reliability. Take, for example, the machines designed to


carve tunnels through mountains where every single metre counts. Irregularities in the rock have the potential to create huge problems for the gigantic drills used, which need to continue to operate even during overload conditions. This is why EAS-HT torque limiting clutches from mayr power transmission are built into tunnel boring machines used around the world. Designed to actuate reliably and traceably, these sustainably protect the drive components from overload damage, the company explains. They cannot be manipulated and the manufacturer-side set torque is accessible even after disengagement. Furthermore, recommissioning is both quick and easy – without requiring additional tools – and the new compact versions can be used as a retrofit solution. Commenting on this, Ralf Epple,


disengagement. The safety aspect is not dependent on recommissioning. The torque limiting clutches also work reliably.”


THE DESIGN Being disengaging element clutches, the range is said to be ideal for applications faced with extremely high torques and speeds, or large mass moments of inertia. They are based on individual overload elements which are integrated into the flanges. The achievable torque results from the pre-tension force of the elements multiplied by the number of elements and the radius at which the individual elements are arranged. Due to the modular concept, the clutches can be tailored to the application; and far higher torques can be managed than with a central disengagement


mechanism, the company explains. While the standard product offers a torque of up to 440,000Nm, the limits of


what is possible have not yet been reached thanks to the modular construction.


The disengaging EAS-HT torque limiters


product manager at mayr power transmission in Mauerstetten, said: “The safety concept must not be susceptible to manipulation. This means that the torque on our clutches is set manufacturer- side and is immediately accessible again after


On the EAS-HT torque limiters, the individual overload elements


transmit the torque through positive locking during functional operation. In case of overload, they separate the input and output faster than any control unit in less than 5ms, almost residual torque-free with high switch-off and repetitive accuracies. Only the friction of the high-quality pressure flange bearing takes effect. The kinetic energy of the rotating mass stored in the system


can slow down freely. Furthermore, the element clutches can be re-engaged simply and quickly. Of benefit, overload clutches can cope with


long slow-down times for the drive following disengagement. “Our clutches are designed so that the bore stroke can, if necessary, be traversed to the end with the clutch disengaged,” explained Epple. The EAS-HT torque limiters are immediately ready for operation after the overload cause has been removed – thay can, in fact, withstand several hundred overload cases. It is also possible to trace at which torque the clutches have disengaged. The new, compact, designs have been specially


developed for the tunnel sector, with 50% weight savings achieved. Each clutch is extensively tested and set exactly to the required value before it leaves the manufacturing site. “In the tunnel and mining branch alone,


we have put several thousand torque limiters into use and have therefore gathered the appropriate experience with regard to the adjustment values,” commented Epple.


SOLUTIONS FOR MANY INDUSTRIES Outside of the tunnel boring industry, Mayr power transmission manufactures safety brakes, torque limiters and shaft couplings, primarily designed for applications in electrically driven machines and systems. They can be found in filling plants, machine tools, packaging and printing machines, as well as in elevators, wind power plants and in stage technology.


mayr power transmission www.mayr.com


16 JUNE 2020 | DESIGN SOLUTIONS 


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