Precise sensors for elevators and lifts

In lifting technologies, as well as in mobile machinery, movement or position monitoring is required for functional and safety reasons. WObit offers reliable Micro-Epsilon sensors as well as Megatron encoders that are used in many measurement tasks to ensure controlled movement sequences.

Encoders

Lifts, cranes and elevators should have a long service life and require almost no maintenance, therefore they must be made with particular attention to quality. This refers to the sensors used in them, which are an important security feature of these machines. In the case of shaft lifts, optoelectronic encoders or Hall sensors are responsible for checking whether the elevator is moving too fast or has stopped and whether it is on the correct floor. They are installed in the glass or on the roof of the cabin, measuring the level at which it is currently located. Inelectric cranesthe position and speed of the cabin are monitored simultaneously based on the measurement results from encoders measuring the speed and direction of motor rotation.

For such applications, WObit offers ETx25 encoders from Megatron equipped with 3D Hall microprocessors. There are three housing versions to choose from: encoders with a full axis for sleeve mounting (ETx25) or flange mounting (ETx25F), each with a standard Ø6 mm axis and a plain bearing, and encoders in a set (ETx25K) for externally mounted axes (flange). The axle with the bearing is made of stainless steel, the housing material is glass fiber reinforced plastic. The encoders have an extremely durable plain bearing with >100 million axis revolutions, continuous axis operating speed is up to 100 rpm, short-term up to 800 rpm. They can operate at temperatures of -40...80 °C, the degree of protection on the axis side is up to IP66. Encoders are available in many variants, which allows the sensor to be optimally adapted to the application and customer needs. Depending on the type of modification, encoders are available from small quantities.

For the most demanding applications, it is also worth paying attention to the FHx58 series of encoders, available in incremental (FHI58) and absolute (FHB58 and FHS58) versions. The high-quality design of the mechanical encoder is independent of the installed sensor technology, and the ball bearings can withstand axis loads of up to 100 N. FHx58 encoders are rated IP67/P69k. The stainless steel encoder body with a special surface treatment, combined with PTFE and TPE sealing elements, allows the FHx58 to be used in applications with high hygiene requirements. In particular, this design allows the FHx58 to be used in saline environments or cleaned with cleaning fluids containing acids and chemicals. FHx58 encoders are designed for an average life of at least 20 years, with a mean time to failure (MTTF) of up to 1,000 years for some electronics.

Cable sensors

Linear sensors measure almost linearly over the entire measuring range and are used for distance and position measurements ranging from 50 mm to 50,000 mm. Micro-Epsilon wire sensors are ideal for both direct integration and subsequent installation in OEM series applications, including: elevators, conveyors and automotive engineering. They measure the linear displacement of the moving part through an attached cable - made of a highly flexible steel braid, which is wound precisely onto a drum driven by a long-life spring motor. The winding drum is axially connected to a multi-turn precision potentiometer or an incremental or absolute encoder. Thanks to this, linear motion is converted into rotational motion, which then causes a change in the resistance of the measuring element or is converted into countable pulses.

Potentiometric wire sensors with integrated electronics have a proportional voltage or current output. Rugged construction and solid, high-quality components guarantee high reliability and long service life - even in difficult industrial conditions.

An interesting application example is the measurement of lifting height in lifting platforms. For lift trucks and elevating work platforms, side supports are used to prevent tipping over. The crane or platform can only be started when the supports are fully extended, so there is no risk of tipping over with long extension frames. However, sometimes this is not possible for space reasons. Therefore, Micro-Epsilon cable sensors are used to measure the extension of the supports. In this way, a dynamic load moment limit is obtained in the actual support area. An excess measurement is performed because it is a safety-relevant measurement value.

Cable sensors are also used to measure the length of mobile crane booms. The current boom length is important in calculating the load torque on the crane. This length is measured using the integrated cable sensor. This simple and telescopic measuring principle makes cable sensors predestined for this task. Sensors can also be modified. For large-range booms, the best solution is the WDS-P200 sensor, which has a measurement range of up to 50 m and linearity of up to 4 mm. The sensor is available with potentiometric, current, voltage, SSI, CANopen, Profibus and incremental outputs.

Precise, synchronized lifting systems are an interesting example of the use of cable sensors. Such systems enable the lifting and lowering of heavy loads in controlled distance and force, or the controlled forward feeding of large components. To achieve this, eight or more actuators are connected to a central high-pressure hydraulic system (700 bar). The displacement of each individual cylinder must be measured as an actual value for synchronized motion and fed to the closed/open loop controller. P60 series wireSENSOR displacement sensors are used for this task.

Cable sensors are also used to measure the lifting height of forklifts, which are responsible for a large part of internal transport. The risk of a forklift tipping over when lifting products is high. Therefore, the permitted speed was limited by limit switches. Micro-Epsilon's cable sensors measure the current lifting height and enable continuous speed adjustments depending on the height of the products.

The examples discussed above are only a small excerpt of the possible applications of Micro-Epsilon and Megatron sensors.Contact our specialists a>who will help you choose the optimal solution.

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