Safety gear
A catching device ( English safety gear ) prevents the crash load at failure of the support means of a hoist .
The lifting and lowering speed is permanently monitored by means of a speed limiter . If the permissible speed is exceeded by a certain amount, the centrifugal governor triggers the safety gear.
When triggered, friction linings (low deceleration) or positive locking wedges (high deceleration) intervene between the lifting carriage and the stationary running rail and thus brake the lifting movement.
Especially when transporting people, the mean deceleration acceleration due to the emergency braking must not exceed three times the acceleration due to gravity for storage and retrieval machines . In the case of passenger lift systems, the permissible acceleration is even lower, which is why adjustable safety gear is used here.
In order to rule out a failure of the safety gear, the speed limiter must be monitored permanently. If, for example, a governor rope is used, rope breakage monitoring is used here.
At speeds over 0.85 m / s according to TRA200 and 0.63 m / s according to EN 81-1 / 2 - apart from a special design - so-called (soft) safety gear is required. Systems built according to EN 81 may have a maximum average delay of 1 g, whereas (old) TRA200 systems can have a maximum of 1.4 g. However, the actual maximum measured delays are significantly higher (up to around nine times).
The safety gear was invented in 1853 by the founder of the Otis elevator company , Elisha Graves Otis .
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- ↑ EN 528 Storage and retrieval machines - Safety , 5.3.4.3, page 13.