A manufacturer of mobile cranes has upgraded its stabiliser‑leg safety system using Contrinex 2‑wire inductive sensors, replacing traditional mechanical contacts with a more reliable, maintenance‑free solution.
The sensors ensure that stabiliser legs are fully retracted before the vehicle can be driven, preventing accidental drive‑away incidents and protecting both operators and equipment.
Mobile cranes, telescopic handlers and similar lifting vehicles rely on extendable stabiliser legs to maintain stability during lifting operations. These hydraulic jacks widen the vehicle’s footprint, preventing tipping when handling heavy loads.
Before the vehicle can be moved, however, it is essential to verify that all stabilisers have been fully retracted. Manufacturers typically achieve this through:
- Cab indicators that alert the operator, or
- Interlocks that prevent the transmission from engaging until the system confirms safe retraction.
The customer’s original system used mechanical limit switches. Although functional, these devices introduced long‑term drawbacks:
- Wear and tear from repeated actuation
- Higher lifetime maintenance costs
- Susceptibility to contamination and environmental conditions
To improve reliability and reduce service requirements, the manufacturer sought a non‑contact sensing solution.
Sensor Solution
Contrinex’s Classic 600 Series inductive sensors provided an ideal upgrade path. The customer selected normally closed, 2‑wire inductive sensors, installing one on each stabiliser cylinder to detect the presence or absence of a target at the fully retracted position.
At first glance, wiring the sensors in series, mirroring the previous mechanical‑contact arrangement, seems logical. However, inductive sensors introduce a challenge: voltage drop across multiple devices in series can compromise performance.
To overcome this, the engineering team adopted a more robust approach:
- Each sensor is configured as normally closed
- All sensors are wired in parallel
- The resulting configuration creates a logical NAND condition
This means the system only confirms a “safe to drive” state when every sensor detects its target correctly. If even one stabiliser leg is not fully retracted, the circuit remains open and the vehicle cannot be moved.
The result
The switch to Contrinex inductive sensors delivers several operational advantages:
- Zero mechanical wear, thanks to non‑contact detection
- Improved long‑term reliability in harsh outdoor environments
- Reduced maintenance costs over the vehicle’s lifetime
- Enhanced safety, ensuring stabilisers are always verified before travel
Click to download Contrinex’s Product Overview brochure to find out more.
Call PLUS Automation on 0121 58 222 58 or email Sales@PLUSAutomation.co.uk
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