Rugged Inductive Sensors Detect Position of Demountable Container on Hooklift Trucks

A hooklift truck utilizes a hydraulic system for loading and unloading a demountable container. Once the container is correctly positioned on the vehicle’s load bed, interlock bolts engage with its base, locking it into position. Rugged sensor systems detect the position of the container prior to activating the locking mechanism, ensuring the bolts will engage correctly; sensors must be mechanically robust and withstand harsh outdoors conditions.

Customer values:

  • Elimination of human error prevents interlock operating until container is correctly loaded
  • Highly reliable sensing performance in highly demanding conditions
  • Corrosion-resistant sensors withstand water, ice, mud and salt
  • Highly cost-effective solution to a potentially serious problem

Specific Product Advantages :

  • Single-piece AISI 303 (V2A) stainless-steel construction
  • Rugged, hermetically sealed embeddable sensors
  • High resistance to harsh operating conditions

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Customer Application

A specialist vehicle builder manufactures hydraulic hooklift systems for commercial trucks. A hooklift truck employs a series of hydraulic rams to hook, lift and pull a demountable container onto the vehicle’s load bed; a full container may weigh up to 30 tons. Hooklift trucks operate all year round, often in harsh environments that include demolition and construction sites.

Hooklift systems are typically semi-automated; the driver positions the truck, engages the hook with the container and initiates the lifting sequence. Once the container is pulled onto the load bed, a pair of interlock bolts, mounted on either side of the truck chassis, actuate and engage with the container body. Once the bolts are fully engaged, the container is locked in position and the truck may be driven safely.

A highly reliable sensor system must detect the position of the container, ensuring that it is correctly loaded before attempting to engage the locking bolts. Sensors must be robust and must withstand water, mud, dirt and ice; they may also be subject to mechanical shock and vibration.

Customer Solution

Rugged Full Inox inductive sensors from the Contrinex Extreme range are designed for exceptionally demanding environments, making them ideal for this application. Highly reliable and rated to IP68/IP69K, these embeddable units feature one-piece AISI 303 (V2A) stainless-steel construction with vacuum-encapsulated electronics, making them well suited to the hostile operating conditions.

During operation, the hydraulic hooklift system lifts the container onto the truck. Two sensors are mounted in the structure of the load bed, one M30-diameter device on a chassis side-member and one M18-diameter device adjacent to the interlock mechanism; the sensors detect the position of the container once it is correctly loaded. Sensing distances of up to 10mm (M18) and up to 20mm (M30) eliminate any risk of accidental collision between the sensors and the container.

With the container in position, the vehicle’s control system deactivates the lifting mechanism and initiates the interlock sequence. Each sensor is configured with an industry-standard PNP normally-open interface; connection to the control system is via an integral M12 connector and PUR-sheathed cable, allowing easy removal and replacement during routine maintenance.

Rugged sensor construction ensures excellent resistance to shock and vibration; these devices are corrosion-resistant and impervious to water ingress, mud, ice and salt. Reliability is excellent; Contrinex inductive sensors deliver a cost-effective solution that satisfies the customer’s requirements for a simple, fit-and-forget system.