Friday 25 June 2010

Sensors unique innovation

An integrated transmitter eliminates the need for an external limit switch with safety clutches
Safety clutches provide precise torque limiting to ensure that the loads on components in machines and facilities do not exceed allowable levels. Up to now they have required an external limit switch and associated cable to send a signal to the controller if an overload situation occurs. The new EAS®-Sensor safety clutch with integrated signal transmitter developed by mayr® Antriebstechnik sends the overload signal wirelessly. This revolutionary and absolutely reliable overload sensing system has considerable advantages compared with conventional signal transmission.

The stroke of a safety clutch when it disengages due to excessive torque is only a few millimetres. This small amount of travel is all that is available to change the state of a built-in mechanical or contactless limit switch. Consequently, external limit switches must be fitted and adjusted precisely and with great care to ensure that they operate reliably. However, under certain conditions even the greatest possible care is in vain, for example when the position of the safety clutch shifts during operation as a result of thermal expansion.

With the new EAS®-Sensor, the limit switch is integrated directly in the clutch. It detects the disengagement motion of the clutch in case of overload and transmits the signal wirelessly to a base station connected to the machine controller. The EAS®-Sensor is adjusted in the factory for proper operation, eliminating the need for assembly and adjustment effort. Overload sensing is fully reliable. External factors such as vibration or axial offset of the clutch, which for example may result from thermal expansion of the shaft, do not impair operational reliability.

The transmitter of the new unit, including its power supply, is entirely contained in the torque adjustment nut of the proven EAS®-compact® safety clutch. It reports the operating state of the clutch at regular, short intervals, along with information on the supply voltage level. If the supply voltage drops, a warning signal is triggered early enough to allow the transmitter battery to be replaced promptly. This does not require dismounting the clutch.

The new sensor is distinctly better than conventional safety clutches with external limit switches, especially in the following application scenarios. In the case of drives with moving shafts, such as robot arms, it is not necessary to move brackets and cable guides along with the drives. This makes the entire assembly significantly simpler and more reliable. Reliable signal transmission is also ensured with drives subjected to vibration or horizontal motion. Axial offset of the clutch, for example as a result of the thermal expansion of the shaft, can easily lead to false triggering in conventional systems with externally fitted signal transmitters. Naturally, the EAS®-Sensor is a perfect choice for applications where there is simply no room to fit an external limit switch. In addition, the new device is an attractive option when drives must be installed on site. It is ready to install out of the box, with no need for prior adjustment by suitably trained staff.

Development of the new sensor has significantly improved the reliability of signal transmission with mechanical safety clutches and substantially simplified the installation of torque-limiting overload protection. Thanks to the integration of the signal transmitter in the proven EAS®-compact® unit, the system not only delivers enhanced signal transmission reliability but also has other quality features that characterise a modern, reliable safety clutch. They include high torsional stiffness, freedom from play, a rapid drop in torque when the overload limit is reached, high accuracy of the adjustable torque, long life, and low life cycle costs. Safety clutches in the EAS®-compact® series fulfil these criteria optimally.

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