Safety chains to prevent window frames from falling

Regina Lau

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Using simple materials of steel chain and clinchnuts, Chair Professor Michael Hung and Dr Ralph Ip of the Department of Manufacturing Engineering and Engineering Management have designed a safety chain fixture that can prevent aluminium windows from falling. The researchers embarked on the project upon invitation by the Housing Department, HKSAR, to tackle the problem of falling window frames, after a number of such incidents occurred in town in recent months.  Easy-to-install and unobtrusive, the safety chain offers a practical and inexpensive quick-fix solution to prevent problematic windows from falling.  


Repeated incidents of falling aluminium windows have caused much alarm and concern about the danger of aging or overloaded window frames, which could pose serious threats to passers-by. CityU’s safety chain device serves as a remedial action to combat the problem. Such a timely applied research initiative once again demonstrates the commitment and dedication of CityU researchers to serve the community.


A safety chain fixture mainly composes of a steel chain, clinchnuts and screws. Laboratory tests have shown that one chain can withstand up to 300 kilograms (approximates 600 lbs) of force. “A standard aluminium window weights about 20 lbs,” said Dr Ip, “Our safety chain is estimated to be able to bear about the weight of 16 window frames.” S-shaped connectors linking window frames and hinges are designed for “good appearance” They become invisible when the windows are closed. The researchers recommend the use of steel and clinchnuts after stringent tests on their capability to withstand tensile stress and shearing force. For monitoring and testing the new device, a household in Kwai Fong Estate has had a prototype fixture installed since 22 July.  


Professor Hung said, “The materials of our safety chain device are remarkably inexpensive, and the installation

distinctly simple. We believe that the fixture will be widely accepted among local households.” Installation of a safety chain takes about five minutes. Two chains are recommended for one window frame. The time needed for completing installation for a household with 10 windows approximates one to two hours. Material cost for one safety chain is less than HK$10.


“Safety chains are merely remedial measures,” said Professor Hung, “To effectively tackle the problem of falling window frames, more work can be done to improve the bar hinge design of aluminium windows.”




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