Black smoke-resistant shaft information system

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Source: CAN Newsletter, Heiko Essinger, Head of R&D, Elgo Electronic GmbH

Example of mounting of Limax33 safe

Limax33 Safe consists of four components: a magnetic tape with absolute encoding, a presence detector for the magnetic tape, the Limax33 RED sensor for determining the absolute position of the elevator cabin, and the Safe Box, in which all switching and control functions are integrated. The encoded magnetic tape is simply installed freely hanging in the elevator shaft using a mounting kit. The integrated safety switch serves to detect the presence of the magnetic tape. The redundant, SIL-3-certified sensor determines the momentary absolute position of the elevator cabin through hall sensors, which scan the encoded magnetic tape contact- free. A wear-free plastic guiding guarantees that the correct distance between the sensor and the magnetic tape is maintained at all times. The position determined by the hall sensors is transmitted via a safe EIA- 485 2-wire interface to a controller or to the Safe Box. Additionally, the sensor has a push-pull output, which is switched inside the door zones of the stored floor positions in order to permit evacuation of the cabin via the control room in case of a stop between two floors. The most important features of the sensor are:

  • Direct, redundant determination of the cabin position,
  • Wear-free, contact-free magnetic measuring principle,
  • Resistance against dirt, dust, smoke and humidity,
  • Ideal for firemen’s lifts,
  • High system resolution of up to 62,5 μm for dynamic position controls,
  • Lifting heights of up to 262 m are possible, speed up to 10 m/s,
  • SIL3-certified according to EN 61508,
  • EIA-485 interface standard, CANopen Safety and other safe interfaces are possible,
  • Easy and quick installation of magnetic tape and sensor,
  • Low-energy 12 V operation.
Integration of Limax33 safe in the safety circuit

As the Safe Box is connected to the sensor via a 2-wire interface, it can be installed either on the cabin roof or in the machine room. This allows the user to minimize the cabling works depending on the type of the elevator. The Safe Box also provides safe inputs and safety relays with normally open contacts. This helps to considerably decrease the number of components and the cabling in the elevator shaft.

The following functions are covered by the overall system:

  • Speed limit, also relative to the distance from the shaft end: saves separate speed limit systems at the shaft end,
  • Door overbridging function: saves floor magnets and floor switches,
  • Limit switch functions: saves safety limit switches,
  • Triggering of clasp break (optional),
  • EN 81-A3 prevention of unintended cabin movements,
  • EN 81-21 reduced heights of shaft pit and shaft head,
  • Teach-in of the floor positions via conventional CAN interface (CiA 406 or CiA 417),
  • Cyclical monitoring of the entire shaft image,
  • Programming of door zone lengths, emergency and inspection limit switch offsets possible up to the limit values defined in EN 81.

Especially in the highrise sector, customer-specific sensors, which are fixed directly in the molding of the rail, are already being used. For this sector, Elgo is currently developing the redundant Limax44 RED sensor, which will include all functional properties of Limax33 RED, but which will work with a sensor-tape distance of up to 12 mm and cover a measuring length of 1500 m. This will permit travelling speeds of up to 18 m/s. The sensor will be interface compatible to Limax33 RED and can also be connected to the Safe Box.