Pepperl+Fuchs Blog

What Are Cable Pulls?

Posted by Robert Pasho on Thu, Jul 05, 2012

When it comes to making rotary encoders work, cable pulls are often the unsung heroes behind the scenes, and you can always count on them.
cable pull

Cable pulls enable rotary encoders to measure linear motion. A cable is wrapped around a spring-loaded measuring drum that turns the encoder's shaft when the cable is pulled in a straight line by the application. Each revolution of the encoder represents a linear movement of the cable equal to the circumference of the measuring drum.
Industries and applications that commonly use this method of measurement include:
  • Mobile equipment: cranes, drilling machines, and excavators
  • Material handling: gates, multilevel shelving rack systems, theater stages, forklifts
  • Automotive: scissor lifts, multilevel conveyors
Material handling applications for cable pulls
These cable-based length-measuring systems have been proven to be very robust, reliable, and accurate at lengths up to 50 meters.

Cable pulls are generally equipped with a mounting face for servo or clamping flange with a coupling mechanism that allows connection to rotary encoders for linear position tracking and feedback. The encoders convert the number of drum revolutions, which is proportional to the measured length, into a digital measuring signal.

The digital measurement signals of position encoders can be output as incremental measurement pulses, but more commonly absolute encoders are used. Absolute encoders are typically available with CANopen, PROFIBUS, EtherNet I/P, DeviceNet, and PROFINET interfaces.

Encoders and cable pulls are often available separately and can be combined for particular applications. Always make sure that the mounting flange styles and shaft sizes for both the cable pull and encoder match.
Encoders and cable pulls are often available separately

Topics: Rotary Encoders

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