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Safety devices
Testing and inspection
All tests and inspections of the safety devices are carried out by qualified in-house personnel. The tests can include up to 1000 test cycles which affect the life of the components, in particular in situations in which, during the rotational motion of the joint-safety device system, the stresses deriving from accelerations and decelerations occur.
The safety devices are complements of the cardan transmissions that are installed between the shaft and the machine, whose function it is to limit the torque peaks and to keep the forces generated within the range of values determined in the design phase, to protect the more delicate components assembled in the machines.
The tests carried out on the test bench make it possible to test the different types of torque limiters: from those consisting of friction discs to those that involve mechanical disengagement. Through the use of appropriate sensors, it is possible to measure the torque delivered which is imparted to the components; the operator can check the values of the forces delivered (which must remain within a range of values established upstream) on a control monitor and evaluate if the device works correctly.
Finally, during the tests overload conditions are reproduced due to the force exerted which will therefore be considerably higher than the actual conditions. For the more advanced components, specific tests are carried out for each piece produced, while for the devices at the base of the range, sample tests are performed with very short intervals for every ten pieces produced.
Devices for each mode of intervention
Torque limiters
Torque limiters can have different intervention modes which can be considered on the basis of customer requests - mostly manufacturers of agricultural machinery - and according to the work to be performed with the machine.
Friction disc torque limiters are clutches that limit the value of the transmitted torque. Their function is to prevent overloads and power peaks from damaging the most delicate components of the machines. This is achieved thanks to the slipping of the friction discs which keep the torque within the set value.
This kind of limiter is recommended to protect the machinery from accidental overloads without torque interruption; the transmission of the power remains within the range envisaged by the calibration and the transmission is always guaranteed without being forced to interrupt the work.
The limiter manages to dampen the transmission overload, keeping the working torque within the calibration range and guarantees working continuity without exceeding the maximum value. Recommended for machines such as cutters that require a damper that limits the torque but is used to continue working, without constantly blocking.
Instead the torque limiter with mechanical release ensures the transmission of torque up to the pre-set calibration value. When the limiter intervenes, it interrupts the transmission of power, completely cancelling the transmitted torque.
The device does not re-engage until the operator removes the cause of the clogging or reduces the speed, bringing the number of revolutions of the transmission to a minimum value such as to allow re-engagement.
In the case of particularly intense stress, the torque can exceed the value set by the calibration. If this happens, the device dampens the torque by not transferring motion, leaving the transmission shaft stationary while the device runs idle; only by decreasing the rotation speed and torque values can the device be re-engaged. These devices are recommended in cases where there is a need to interrupt the torque and therefore to immediately stop the machine following an overload to safeguard both the machine and the driveshaft which could otherwise suffer compromising damage.
Devices for each mode of intervention
Torque limiters
Eurocardan has a dynamic bench which is used to replicate the actual operating conditions and to artificially activate the safety devices. Specifically, a motor with a power of over 300 Hp is used to which a hydraulic disc brake is connected which, intervening, simulates the flooding that could occur during operational use of the vehicle. The test is carried out when the equipment to which the driveshaft is connected rotates at maximum power: the brake is activated, generating flooding, at which point the reaction of the safety device is tested during blocking of the motion transmission.
The automatic IDR device represents the most advanced Eurocardan system. In fact, it was designed to lock the part connected to the brake, which simulates the equipment, and remains stationary, while the part that simulates the tractor connected to the machine continues to turn. Therefore, both torque delivery and rotational motion are stopped completely; until the number of revolutions is reduced and the cause of the flooding is removed (in our case the brake) automatic re-engagement will not take place.
