Limax Lift Technology in One WTC

Elgo Electronic GmbH & Co. KG supplies its Limax sensor technology to elevators in One World Trade Center (WTC)

Elgo Electronic GmbH & Co. KG of Germany has supplied its Limax sensor technology to 30 passenger elevators in the One World Trade Center (WTC) building in New York City. Elgo also manufactures other magnetic-based length-measuring systems for the lift industry and has installed Limax sensors in more than 27,000 elevators worldwide. It’s U.S. company, Elgo Electronic, Inc. is located in Bartlett, Illinois. Designed for position determination, the sensors enable elevators to travel at speeds greater than 10 mps.

The technology for determining positions by using sensors and a corresponding magnetic tape has been a reliable part of the elevator industry for many years. In addition to its compliance with relevant safety norms, the ease and speed of installation also plays an important role in the design of elevator technology. The magnetic tape, which contains the code for position determination, is first installed in each elevator shaft directly on one of the guide rails for the elevator car with an adhesive tape. The tape consists of two layers; one is a magnetized plastic tape carrying the information, and the second is a magnetically nonconductive and flexible steel tape called “conclusion tape.” The steel tape provides mechanical stability to the entire system and protects the plastic tape from mechanical damage; however, it is a magnetic short circuit, which can increase the functional safety under extreme mechanical conditions. In One WTC, 9,000 m of Elgo’s magnetic tape was used in the elevator shafts.

The difference between various measuring systems is the type of code encoded on the tape. For the Limax series, this is known as “absolute code.” In it, the magnetic plastic layer is encoded with a pseudo random code, which consists of randomly alternating north and south poles. The sensor is typically installed on the elevator car; however, for One WTC, it was installed on a sledge and reads out the code from the tape without direct contact.

An electronic system in combination with the corresponding software can continuously determine the exact position of the elevator cabin and transmit this information to the control unit. The information triggers actions such as driving off, slowing down the car, stopping correctly within door zones and opening doors, in addition to various other elevator operations. One of the most important advantages of an absolute measuring system is that the position will not be lost in a power failure. When the elevator is placed back into operation, the exact position of the cabin can be immediately transmitted to the controller. This can provide additional safety and nullifies the need for calibration processes.

In addition to high traveling speeds, another distinctive feature is that the position of the elevator car is detected without contact. In systems not subject to friction during operation, there is no disruptive noise. Specifically, in belt-driven positioning systems, higher speeds often cause increased buzzing and high-frequency and other disturbing noises. Furthermore, this type of contact-less measurement is not subject to abrasion. This can make the replacement of guiding or gliding surfaces in the context of maintenance unnecessary. Both the sensor and magnetic tape have an extended operating life, thereby contributing to safety.

For more information, contact Alexander Scherr of Elgo at e-mail: alexander.scherr@elgo-electronic.com or website: www.elgo-electronic.com.