Find out how inductive sensors detect the position of forklift fork when opening the container lid!

Find out how inductive sensors detect the position of forklift fork when opening the container lid!


A container manufacturer uses a modified forklift, fitted with two sets of forks, for unloading bulk cargo. The lower forks support the container while the upper forks control the lid. When unloading, the lid opens and the lower forks rotate, tipping out the contents. A robust inductive sensor senses the position of the lid, ensuring it opens fully before emptying.


Containers are often used when transporting bulk cargo, including wood chip and biomass, by rail. A Swiss manufacturer of bulk-cargo containers has developed an innovative unloading system that uses only a modified forklift, eliminating the need for specialist handling equipment.

The forklift has two pairs of lifting forks. The main forks, mounted conventionally, support the weight of the container as it is unloaded from a freight wagon; a second pair, mounted vertically above the lower pair, opens and closes the lid of the container. During opening, the upper forks lift the lid a short distance before tilting it vertically, leaving the top of the container completely unobstructed.

The lower forks then rotate about a horizontal axis, tilting the container end-over-end and tipping the contents out. A robust and reliable sensor system is required to detect the vertical position of the lid before rotation begins. An extended sensing distance is essential to eliminate the possibility of mechanical damage.


A metal bracket is mounted externally on the actuating mechanism for the upper forks; the embeddable sensor is mounted immediately adjacent to one of the forks and detects the position of the actuating arm as it drives the fork into the vertical position. The AISI 303/V2A stainless-steel housing and sensing face are corrosion-resistant and impervious to water ingress; the sensor is IP68- and IP69K-rated.

Configured with an industry-standard PNP normally-open interface, the Contrinex M30 Extreme sensor connects to the forklift’s lower-fork tilt-control systems via a flexible PUR-sheathed cable. A sealed cable entry ensures fit-and-forget capability during extended periods of operation in an outdoor environment.

The Full Inox inductive sensor detects the vertical position of the forklift’s upper forks effectively and repeatedly, ensuring safe, reliable operation of the unloading system. Contrinex inductive sensors deliver a cost-effective solution that satisfies the customer’s requirements for extreme robustness and extended sensing distance.

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18th Dec 2018 S.Abedi

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