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world of industries 8/2016 (EN)

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world of industries 8/2016 (EN)

Disengaging torque

Disengaging torque limiters with automatic re-engagement MDA INDIA Today’s machines are becoming increasingly compact and making it harder to access the drives. And yet these are the exact machines that require reliable overload protection. A new, dis-engaging torque limiter re-engages automatically by rotating backwards slowly. In applications where hard rocks and stones are burst into pieces or machines that cut their way through rock, only robust and solid torque limiters can survive this extreme levels strain. The frequently tough operating and ambient conditions in heavy mechanical engineering such as dust, water spray, heat or cold, not only places the strain on the workers in these plants, but also on the individual components of the drive line. In particular due to these rough ambient conditions, the drive lines in these machines are frequently encapsulated and therefore hard to access. The company, Mayr power transmission, as an expert on clutches and brakes, has developed a robust torque limiter ‘the EAS-reverse’, which is able to cope with such high strains and also re-engages automatically – ideal for drives which cannot be accessed for re-engagement purposes. These torque limiters protect large machines permanently and reliably against damage due to overload, and thus ensure the operational safety and maximum productivity of these large systems. Patented technology and unique functional principle Norbert Vogl, developer at Mayr power transmission explains “On the new EAS-reverse torque limiter, all functional processes can be automated via the drive. This is a disengaging clutch which automatically re-engages simply by rotating backwards slowly, without the use of pneumatics or hydraulics”. Double cylindrical rollers function as torque transmission elements on the EAS-reverse. They ensure an exceptionally robust torque transmission and favourable contact conditions. On re-engagement, the double rollers are characterised by high rolling contact and therefore low friction contact. “Due to the low friction contact, the clutch has a favourable service factor. This service factor is also positively influenced in that the EAS-reverse works with a direct torque transmission mechanism of high rigidity, which means that an additional disengagement mechanism is not required” says Norbert Vogl. The torque transmission is conducted with exceptionally low backlash (< 0.05 °). All functional parts of the clutch are hardened. Instant disengagement, immediate drop in torque In case of overload, if the torque exceeds the value set on the clutch, the EAS-reverse disconnects the input and output with high switchoff and repetitive accuracy within split seconds nearly residual torque-free. The kinetic energy of the rotating masses stored in the system can run out freely. Through the use of cup springs with a negative characteristic curve, the torque drops immediately. The 20 World of Industries 8/2016

MACHINE ELEMENTS Mayr power transmission’s new robust torque limiter which is able to withstand high levels of strain and tough ambient conditions, and also re-engage automatically – ideal for drive lines in heavy mechanical engineering which are hard to access so-called pumping or breathing of the clutch is thus excluded, and the wear on the disengagement mechanism is low. The EAS-reverse torque limiter can withstand long drive run-out times after being triggered. When defining the permitted run-out time, only the robust double bearing on the clutch must be considered. It is necessary to switch off the drive soon after disengagement of the clutch, but targeted braking of the motors is not required. The overload signal, for example, is supplied by a contactless limit switch, which permanently monitors the operating condition of the clutch. Due to the complete disconnection of the input and output, no engagement impacts occur during the over-travel time, which might have a negative effect on the drive line. The clutch is re-engaged by reversing the direction of rotation at a speed of < 10 rpm. Flexible and customizable with various possible combinations Mayr’s new EAS-reverse torque limiter is easy to handle and has numerous versions and additional features for tailored, branchoptimised solutions. For example, the combination with an elastomer clutch permits simple disconnection of the drive line by loosening a few screws, without having to displace the motor or gears. In addition, a combination with brake disk can be provided for loadholding output applications. The EAS-reverse can also be easily integrated into a solid housing with Standard IEC or NEMA-dimensions, thus rendering it dust and spray proof, water-proof, and protecting it effectively against adverse ambient conditions. The standard series EAS-reverse can be used within a temperature range of - 20 to + 40 °C, extensions to temperatures from -30 to + 80 °C are possible. The new torque limiter has up to now with its initial three construction sizes covered a torque range of 80 to 2,500 Nm, and is about to be extended by a fourth construction size up to 5,000 Nm and a bore diameter up to 100 mm. About Mayr power transmission Founded in 1897, Mayr power transmission is a family-run company based in Mauerstetten, in the Allgäu region of Germany. Mayr is leading manufacturer of safety brakes, torque limiters and shaft couplings. These products are primarily designed for application in electrically driven machines and systems. They can be found, for example, in filling plants, in machine tools, in packaging and printing machines as well as in elevators, in wind power plants and in stage technology. Currently, approximately 600 employees work at its headquarters in Germany. Worldwide, Mayr power transmission has more than 1000 employees. With production plants in Poland and China, sales subsidiaries in the USA, in France, Great Britain, Italy, Singapore and in Switzerland as well as 36 additional country representatives. Before a clutch leaves the Mayr power transmission factory in Mauerstetten, it is comprehensively tested and set precisely to the required value. The company has diverse, modern testing equipment and profits from decades of experience. An electronic database in which the measurement values are archived together with the associated serial number of the product guarantees 100 % traceability. Photographs: Chr. Mayr GmbH + Co. KG, lead: shutterstock/weareone 01 The EAS-reverse with patented disengagement mechanism – ideal for drives which cannot be accessed for re-engagement 02 The EAS-reverse: easy to handle, permits long run-out times and resistant to dust or water spray 03 Combining the EAS-reverse with an elastomer coupling permits easy separation of the drive line by loosening a few screws without having to displace the motor or gears 04 With its various versions and features, the EAS-reverse is extremely customizable. For example, in combination with a brake disk 01 02 03 04 World of Industries 8/2016 21