Long travel position feedback with CAN SAE 1939 comms: Combilift’s CSS container loading system uses Variohm EuroSensor supplied cable extension transducers

Combilift, based in Co. Monaghan – Ireland, is the largest global manufacturer of multi-directional forklifts and an innovator and leader in long-load handling solutions. Its recently launched Combi- CSS (Container Slip-Sheet) enables fast and efficient freight container loading for the transportation of timber, flat-packed furniture, panel products and similar goods. This innovative system features a large platform where goods are pre-loaded on a powered steel slip-sheet, and with integral laser-assisted container alignment and hydraulic levelling the slip sheet and its payload are driven directly into the container hold using Combilift’s patented push-pull mechanism. Significantly reducing the full load loading time to as little as 6 minutes and ensuring safety and simplifying the loading process, the Combi-CSS control system relies on SGJ series cable extension transducers (CETs) from Variohm EuroSensor to monitor the slip-sheet’s position over CAN SAE 1939 for the loading and retracting procedure.

The 16-metre-long Combi-CSS is capable of loading up to 30,000kg in 20- to 40-foot containers with the alignment and load transfer process managed by a single operator. The slip-sheet material, Hardox 500, is an extremely hard grade of steel commonly used for large structural wear plate components in construction and mining equipment. With excellent resistance to scratching and surface scraping, these properties help maintain a low sliding friction for the loading and sheet retraction process. The slip-sheet has several pairs of holes at equal intervals along its length and the push pull mechanism, which sits underneath, utilises powerful hydraulically driven linear actuators that engage with these holes in an alternating pattern to drive the sheet forwards for loading or backwards to retrieve the sheet. The distance travelled by the actuators for each push or pull cycle determines how far the slip sheet travels – with position controlled using displacement feedback from the SGJ series cable extension transducer.

The SGJ series CET from Variohm’s distribution partner TE Connectivity Inc., was chosen for its industrial grade quality and IP67 environmental protection rating. Its rugged glass-filled polycarbonate housing protects a precision high-cycle plastic hybrid rotary potentiometer in a spring-loaded cable and winding drum arrangement. The durable stainless-steel measuring cable is simply attached to the moving element in a "free-release" tolerant design that safeguards against damage if the cable is accidentally released. A stainless-steel mounting bracket and industry standard M12 connector makes installation straightforward in any orientation.

With several output options available in the SG series, including voltage and current as well as CANopen versions, Combilift chose the SGJ model with an integrated CAN SAE J1939 output communication profile – which is widely used on mobile equipment and factory automation applications and interfaced seamlessly with the CSS’s control system. The zero to 80-inch measurement version (2032 mm) provides an accuracy of 0.5% and a full-scale repeatability to 0.02%. The position data, in 12-bit resolution, and device status information is transmitted as ‘Proprietary B’ messages over the J1939 network. The Node ID, baud rate and date rate options are easily set using dip-switches and versions are available with or without terminal resistors. The 80-inch travel version can be mounted in a volume of less than 100 x 67 x 127 mm; a larger 120-inch travel version is also available.

CETs, sometimes referred to as ‘String pot sensors’ provide a cost-effective technology for long travel linear displacement measurement and find use across industrial applications such as mobile construction and forklift vehicle safety monitoring, winch and crane position feedback, large agricultural machines, flood management systems etc. Variohm supplies CETs in miniature designs with position measurement as small as 40 mm through to long travel models with over 40 metres linear measurement capability. The sensors used in CETs include rotary potentiometers, incremental encoders and multi-turn absolute encoders. Output options cover all industry standard voltage and current output levels as well as digital pulse and bus communication protocols. Cable actuated technology requires no critical alignment and suits applications where space is limited or where moving components may be submerged, deep underground or partially obscured by other equipment. Variohm’s comprehensive range of CETs are easily adapted for use in harsh environmental conditions with IP68 protection ratings and application matched versions supplied with hazardous area certification.

Variohm EuroSensor is a distribution partner to leading sensor suppliers and with its own design and manufacturing capability supplies a wide range of position, force, pressure, load, and temperature sensor technologies for demanding measurement application solutions in industry, construction, agriculture, motorsports, medical, research and more. For more information on Variohm’s cable extension transducer range visit www,variohm.com.

About Variohm EuroSensor

Variohm EuroSensor is a manufacturer, distributor and supply chain partner providing complete sales and application support across a comprehensive range of position, force, pressure, load, and temperature sensor technologies - for demanding measurement applications across industry, construction, agriculture, motorsports, research and more.