Page 14 - Industrial Terchnology EXTA 22nd March 2021

Through the transparent window, they can then
watch the production process.”
The ingredients are stored in special
containers on five levels. A gripper arm brings
the cup to the selected ingredients, opens the
lids of the containers and pours the
ingredients into the cup accurate to the
gram. Then the cup is sealed, labeled,
shaken and provided via the output tray.

Holding safely in position
The gripper arm, or the vertical axis, with
which the cereal cup is moved up and
down, is powered by a step motor, which is
equipped with a ROBA-stop-M safety brake
from Mayr Power Transmission. Once the
motor has moved to a certain position, the
brake holds it with millimetre precision, and
reliably. This means, the brake works as a
holding brake in normal operation, but it can
also reliably stop the cup during movement in
an emergency.
This is because the ROBA-stop-M brakes are
fail-safe electromagnetic safety brakes. They are
closed in de-energised condition, ie after a power
failure or emergency stop. When the power is
switched on, a magnetic field builds up in the significant energy savings, as the brake is only
brakes. The armature disk is attracted to the coil energised with high voltage for a short time when it
carrier against the spring pressure. This releases the is switched on. In this phase, a high magnetic force
rotor, ie the brake is released. In the event of is required to attract the armature disk via the air
malfunctions such as power failure or emergency gap.
stop, the ROBA-stop-M brake reliably brings the However, once the armature disk is in contact
gripper arm with the cup to a standstill within a very with the coil carrier, significantly less magnetic force
short period of time. This protects the vending is sufficient to keep the brake open. For this reason,
machine from damage and downtime. the voltage can be significantly reduced in this
phase. Most of the energy saving potential of the
Controlling brakes intelligently ROBA-switch rectifier is based on this behaviour:
In order to reduce the operating temperature and ratios of up to 4:1 between pull-in voltage and
the energy consumption of the muesli vending holding voltage are possible.
machines, the safety brakes are used together with If the rectifier lowers the voltage to a quarter of
a Mayr ROBA-switch rectifier. This allows the value after the brake is released, the coil

March 2021 • INDUSTRIAL TECHNOLOGY EXTRA • p14