A contract to develop a solenoid-actuated shutter latch for portable building windows expanded into a full system-wide project for Magnet Schultz Ltd (MSL), the UK’s authority on electromagnetic actuator applications. The concept originated from a requirement from Skelmersdale-based Stackright, one of the industry’s leading portable accommodation manufacturers. MSL designed the system solution in conjunction with Stackright, and is able to adapt the automatic window closure technology to other applications
The new safety system for Stackright’s portable accommodation units is designed to automatically activate window closures in the event of a fire, to prevent it spreading to adjacent cabins. Fire rated accommodation units must satisfy the directives detailed in a joint code of practice for fire prevention on construction sites. Low-power shutter latches are at the sharp end of the system. When activated, these innovative devices – designed by MSL expressly for this application – operate an integral low-power ‘energise-to-release’ solenoid to disengage from the heavy-duty metal shutters fitted to cabin windows.
The spring-loaded shutter closure mechanism was also developed by MSL. It deploys a torsion spring force that limits the closing acceleration but delivers enough hold-closed force to meet regulations without endangering the safety of nearby personnel. At the heart of the system is a control panel designed by Magnet Schultz Ltd. It provides the central intelligence required to meet a specific set of goals: to be triggered automatically by a fire; to signal an evacuation alarm; and then to automatically enter a containment mode to prevent the fire spreading.
Previous incarnations of latches used on portable cabin windows deployed energise-to-hold magnets. “This is not an energy inefficient solution,” explains MSL Managing Director Andrew Newton. “From 40 years of experience, we knew that a special-purpose electric latch would be a better option for shutter operation, both for technical and commercial reasons.”
Many of MSL’s design and prototype projects focus on the electromagnetic subassembly. This collaboration with Stackright was different. “We undertook the development of the entire system to deliver a complete, tested and ready-to-install solution by extending our project management skills to encompass a system rather than simply a product used within a system,” says Newton.
The automated system meets the directives of the Joint Code of Practice. Each pair of shutters overlap for added security and fire proofing, so the closing mechanism releases one latch before the other in a two-stage process. In addition, the master controller provides operational, power monitoring and intuitive alarm sounder functions, plus at-a-glance LED status indicators. This panel also allows a building complex to be rapidly locked down manually by hitting an emergency button – a function also used to test the system.
The solenoid shutter latches feature ultra-low power release, requiring only a short duration, low current activation signal from the controller. Such energy efficiency contributes to the very low overall power consumption that allows the entire system to be battery powered. “This was a design goal as we cannot rely on a construction site having a ready supply of mains power supply,” explains Newton. “Mains electricity is only used to keep the batteries charged, and these can last 48 hours without recharging.”