FEATURE CLUTCHES, BRAKES & COUPLINGS
Safety brakes take centre stage in theatre productions
Elaborately designed stage sets need safety brakes to protect the actors from heavy stage elements, which is why mayr power transmission has introduced the new ROBA-stop-stage series, as Peter Lucke, area sales manager, explains
A
wide variety of industrial applications rely on safety brakes from mayr power transmission – from machine tools to crane systems and
robots – but these components are also used for an important role within the theatre industry where elaborately designed stage sets are often used. During a performance, the hoists of the upper machinery hold and move often quite heavy stage elements, decoration and lighting units, above the heads of the artists with millimeter precision; and they are sometimes even used to transport people. Special safety requirements are a necessity here, meeting DIN 56950 (BGV C1) and the new standard DIN EN 17206. If the power fails or an emergency stop is needed, the safety brakes
in the stage drives bring the loads to a standstill as quickly as possible. To reliably protect the actors on stage from falling loads, the drives are usually equipped with either two brakes or one brake with two brake circuits that operate independently of each other. Both the brakes are capable of holding the load safely on its own, thus ensuring that even if one brake fails, there is no danger. However, when both brakes work properly, this concept leads to a doubling of the braking torque during emergency braking and thus to a considerable strain on all components – the keyword being accident load. In order to comply with the applicable safety regulations, the stage constructions are regularly tested and approved, showing that defects on ropes, rollers or cross beams can be caused by the accident load. As a consequence, the structures must either be dismantled or the hoists must be moved more slowly. There is, however, a new solution from mayr power transmission
– the new generation of stage brakes: the ROBA-stop-stage series. These operate without doubling the braking torque in the event of an emergency stop, while at the same time ensuring maximum safety for personnel and material.
A NEW SOLUTION Bernd Kees, product manager at mayr power transmission in Mauerstetten, explained: “The ROBA-stop-stage brakes have two individual brake circuits. This way they achieve the necessary redundancy. However, the special design means that the braking torque is not doubled during braking. The brakes work softly and are gentle on the components.” Not only are they compact, but thanks to their
lower braking torque it is possible to reduce the overall size of the systems enabling, for example, a smaller gearbox size to be selected. Furthermore, these are now certified by TÜV Süd and have already been in use in a similar form for a major customer, so have therefore been tested under real-life conditions. Delivered assembled and adjusted, the brakes can be installed quickly
and easily, while eliminating adjustment errors. In operation, they are both quiet and maintenance-free, a real benefit for theatres and opera houses. Of further benefit, the stage brakes feature a plug-in hand release, allowing both brake circuits to be opened at the same time in an emergency. During operation, however, the hand release is removed to prevent accidents – for example, due to incorrect operation.
36 MAY 2021 | DESIGN SOLUTIONS
To fulfil safety standards requirements, an indispensable element for
safety brakes is an integrated function monitoring system which provides feedback on the switching condition of the brake. This ‘release monitoring’ prevents un-permitted operating conditions, such as the motor starting up against closed brakes, for example. For this purpose, the ROBA-stop- stage brakes are equipped with the company’s proven contactless release monitoring, which it has been offering as an alternative to release monitoring with microswitches for a number of years. The contactless system with inductive proximity switch enables the control system to record and evaluate the operating condition of the brake, meaning that the control system allows the motor to start up only after brake release. The contactless release monitoring is also resistant to magnetic fields, impacts and vibrations, as there are no movable parts, and the electronics are completely encapsulated. It is also reliable and guarantees maximum functional and operational safety – after all, during a performance, when the decorations are moved every second to match the music, for example, the technical background must function smoothly and reliably. The contactless release monitoring system is not only less susceptible to malfunctions, but also has no wear-prone switching contacts such as microswitches.
BRAKE TRACEABILITY During the brake manufacturing process, the company not only ensures that their design eliminates possible adjustment errors from the start, but also carries out a careful final inspection. This means that every single safety brake which leaves
the plant is subjected to a 100% inspection following complete assembly and adjustment. During the course of the inspection, function-relevant parameters such as pull-in and drop-out voltages, coil resistance, dielectric strength of the coil, insulation of the coil to the housing, axial force, armature disk stroke, and the operating principle of the switching condition monitoring, are determined. All the determined measurement values are archived together with the corresponding serial numbers of the brakes in an electronic database. This ensures 100% traceability.
mayr power transmission
www.mayr.com/en / DESIGNSOLUTIONS
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