An Engineer in Wonderland – There aren’t ‘arf some clever…

eiwsnaptop3.jpg Occasionally I get that I-wish-I’d-thought-of-that feeling. And these cunning little tins produce exactly that. The lid is firmly attached until by pressing the centre of the lid, the lid suddenly snaps down. It moves a millimetre or so and, by distortions in the metal I never expect to understand, the clips around the edge spring apart allowing the lid to be lifted away.

I measured the force with the post room scales and it turns out to be an effortless-feeling 2.2kg (21.5N for pedants). Similarly 1.2kg applied sideways to the clips snaps the top back on. Neat, simple, functional. Admittedly, some work better than others, and a few are barely bistable, but that does not detract from the essential brilliance of the idea. How anyone ever invented this mechanism, let alone got it to work with so little movement and so little force, is beyond me. eiwsnaptop1.jpg If there are mechanisms or circuits that similarly inspire you? Get in touch, via the Comments field below. Alice (special contributor) By the way, the title An Engineer in Wonderland was inspired by the 1967 book ‘The Engineer in Wonderland’ by Professor Eric Laithwaite: champion of the linear induction motor.

Tags: engineer

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1 Comment

  1. March 20, 2008 16:44

    When I were a lad in the 50’s…
    Those clever little lids were used on 1 gallon [4.5 litre] oil cans to seal the top. A paper washer underneath was compressed when the sides were squeezed in and opening was so easy, just press the top. Instant reclosure.
    Security in transit was handled by a thin tinfoil cover with a tear tab that prevented the side wings expanding.
    The same technology [more often in plastic than in metal] is used in key boards & pads for providing tactile feeedback and as kids we had litle metal devices called “clickers” to annoy people with.
    Lastly, a distant relative is the “Belleville washer” a dished washer used as a spring with small movement and high force. Often used in press work and similar applications.

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