In the movie hit Spiderman the comic hero flies in the action scenes through the New York street canyons. For the recording of such scenes one uses so-called flying machines. Stage winches move the stuntmen on thin wire ropes through the air. Stage winches are also used in theaters, music houses or on concert stages to move scenery, curtains or heavy floodlights, lift and lower. To protect the actors such winds with redundant safety brakes of mayr drive technology equipped specifically for stage technology applications.
In addition to the "Roba-stop-silenzio", The quietest stage brakes on the market, are among others also the grinding-free, noise-dampened caliper brakes of the series "Roba-diskstop"Very good for stage technical applications. They can be arranged very flexibly on brake discs. Size and number of brakes determine the achievable braking torque. As a rule, two brakes are used in stage winches, which work completely independently of each other. Each of the two brakes alone is able to hold the load reliably.
This ensures that even if one brake fails, there is no danger for the actors. If both brakes work, however, this concept leads to a doubling of the braking torque during emergency braking. An American manufacturer placed six single Roba-diskstop pliers brakes on the brake disc of a stage winch. First and foremost, the high number of brakes is necessary to achieve the required braking torque.
One brake replaces the other
However, the arrangement of several brakes also has an interesting positive side effect. As with systems with two brake circuits, one brake has the task of compensating for the failure of another brake. An additional brake is thus sufficient to meet the requirement for redundancy. The other five brakes bring together the required braking torque, so each only 20%. If all six brakes are intact, the system will delay 120% of the nominal braking torque during emergency braking. The brake torque increase is not 100% as in systems with two brake circuits, but only 20%. The braking process is much gentler and less stressful for the peripheral components. The Roba-diskstop is in de-energized state, so even with emergency stop or power failure, closed. When energizing the solenoid coil an armature plate is pulled against the force of the coil springs to the bobbin; the brake is released. A microswitch monitors the ventilation. This prevents the drive from starting before the brake is opened. The built-in manual release allows mechanical opening of the de-energized brake for inspection or maintenance.
Floating storage of the brake
Such modern, floating mounted caliper brakes are state of the art today and are also widely accepted in stage technology. They are considered robust and extremely reliable. In practice, however, it has been found that by slight contact of the friction linings on the rotating brake disc noise may occur. Due to the floating bearing of the brake and the magnetic effect - caused by the energized coil - the brake follows the movement of the brake disc. This behavior results in a slight amount of drag, which causes noise that can not be accepted in many stage technology applications. Therefore, the Roba-diskstop safety brakes of the described stage winch were equipped with an exemption. It ensures that when the brake is open on both the left and on the right side of the brake disc, a uniform air gap is present. Even with uneven wear of the friction linings, this patented design ensures that the brake disc can rotate between the two friction linings without friction when the brake is open due to the uniform air gap.
Influences on the noise behavior
Before the "invention" of the exemption was trying to get the problem by exact adjustment of the air gap in the handle. That did not work reliably. However, as already mentioned, continuous grinding can also be created solely by the magnetic attraction between the armature disk of the brake and the brake disk. Other factors influencing the air gap and the so-called "blow" of the brake disc. The smaller the air gap and the larger the impact, the higher the risk that the brake disc will drag and cause noise when the brake is released.
Some brake providers sometimes work with very small air gaps to keep the switching noise low. The Roba-diskstop works with a relatively large air gap and still switches extremely quietly. It is equipped with a highly effective patented noise damping system, which keeps the switching noises even with lining wear and thereby increasing air gap. Mayr Antriebstechnik offers completely different brake systems for all modern stage technology applications.