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Three-beam light guards offer more for less

20 December, 2009

At the recent SPS/IPC/Drives show, Leuze electronic launched a range of three-beam light beam safety guards which are designed to replace traditional four-beam systems and to offer more features than their predecessors, but at a lower price. The MLD 300 (Type 2, SIL2, PLd) and MLD 500 (Type 4, SIL3, PLe) devices save space, complexity and cost by integrating electronics into their end-caps and avoiding cabling on one side of the guard.

Traditionally, safety light beam transceivers have used two or four beams with reflecting columns that act like periscopes. A mirror reflects the incoming signal down the inside of the column and back out to the receiver from a mirror at the bottom. A four-beam system consists of a pair of two-beam systems: one in the top half of the column; the other in the bottom half.

In many applications, two-beam systems do not protect machinery adequately and four-beam systems are needed to produce a middle beam.

Leuze’s new three-beam transceivers (above) use a technology derived from its multibeam light curtains to switch two transmission beams precisely so that they can be detected and identified by a single receiver. This cuts manufacturing costs, which combined with other design features such as optics in the end-caps, allows the MLD devices to offer more features for less money than their predecessors.

They are suitable for applications from simple access guarding, to safeguarding combined with muting – for example, at points where pallets leave guarded areas – as well as wide-area guarding of perimeters up to 70m long.

Within the MLD300 and MLD500 ranges, there are three levels of functionality. The most basic MLD 310 and MLD 510 models offer functions such as automatic reset and LED displays. The MLD 320 and MLD 520 models add start/restart interlock, contactor monitoring and configurable operating modes. The top MLD 330 and MLD 530 models provide integrated control of parallel or sequential muting and include muting indicators and digital readouts. Features are selected making direct connections, without needing to use a PC.

The two- and three-beam transceivers have 8m ranges. The family also includes two-, three- and four-beam transmitter and receiver systems with 70m ranges.

Installation is made easier by a patented mounting system which allows a wide choice of mounting heights rather than being constrained by pre-drilled mounting holes.  

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