The new electromagnetic linear brake ROBA-linearstop from Mayr Power Transmission offers a fail-safe system with high holding forces, which can also brake dynamically and provide short switching times.
Safety brakes, which influence separate round rods or piston rods or on guide rails, are often used to safeguard linear movements. Depending on the application, pneumatically or hydraulically opening brakes, that reach high holding forces, are often used for this purpose. But drive axles are nowadays increasingly equipped with electric motors. Purely electrical systems – also for safeguarding – are the trend.
“We offer electrically opening linear brakes which are also safety brakes,” said Bernd Kees, product manager at Mayr Power Transmission. This means, the brakes operate according to the fail-safe principle. They generate the braking force through thrust springs and are closed in de-energized condition. The new series of electromagnetic ROBA-linearstop brakes comprises six construction sizes with forces ranging from 70 to 17,000 N.
“Most linear brakes available on the market today serve as static clamping units and have been designed to hold the axes safely at a standstill,” said Kees. “However, there might be people under suspended loads during initial operation, maintenance or even during the production process without the load transfer to the mechanical linear brake having taken place first.”
If the drive fails completely during these operating conditions, the linear brake alone is responsible for the reliable deceleration of the load. Which is why the safety brakes are also designed for such dynamic braking situations. The company has voluntarily subjected the brakes to a type of examination as a safety component in accordance with the Machinery Directive (2006/42/EC).
On vertical axes, short stopping distances are important for the safety of people and machines. The brake switching times are decisive for the braking distance, as during the free-fall time until the brake closes and the retardation takes effect, the mass additionally accelerates. The new electromagnetic linear brakes therefore impress with their short switching times.
“In comparison to previously common products, our brakes switch faster by a factor of 10,” added Kees. However, maximum safety is only achieved if the projected switching times are guaranteed over the entire service lifetime. Therefore, reliable switching condition monitoring is key. In the new electromagnetic ROBA-linearstop brakes, the control module is used for this purpose. For larger brakes (from construction size 40), monitoring with proximity switch is also possible.
In addition to linear brakes for piston rods, Mayr Power Transmission is currently working on electric safety brakes for profiled rails.