Safety first at the front door
The Englishman’s home may be his castle, but most homes have an aperture of vulnerability in the form of their letterbox
A common problem is that many letterboxes admit rain and draughts. In extreme cases, people have died when petrol has been poured through their front door letterbox and ignited. And if the door latch is near the letterbox, thieves have been known to insert coat hangers to unhook the latch and do a quick burglary. A common approach is to equip the flap with a strong spring, but this does nothing to prevent arson attacks and coat hanger thieves, and usually only leads to trapped fingers and damaged letters.
A box on the back of the letterbox solves some problems but if the flap does not seal perfectly well, can result in rain seeping in and soaking the letters in the bottom of the box. It also provides an opportunity for the unscrupulous to insert a pair of tongs and retrieve the letters for identity theft or other dishonest purposes.
Our challenge this month is to come up with a design for a better letterbox, which will protect the house or apartment and the letters – but without having a hand-trap letter flap with powerful spring on the front.
The solution adopted by the very rich and powerful – to dispense with the letterbox completely, because there is always a flunky on the inside to open the door when the post arrives – is not available to the ordinary citizen.
CCTVs aimed at the front door are only useful if somebody is watching them at the right time, and internal automatic fire extinguishers and alarm sensors are not a sensible option for the homeowner. Anything that requires a lot of complexity adds not only cost but also potential unreliability. The solution should be simple, low cost and reliable. The one below solves the problem elegantly and at low cost without using any kind of electronics. Once you see it, you will consider it obvious – though it is innovative enough to be protected by patent. For those without access to the web, the solution will be described fully in our September edition.
The solution to this month's challenge comes from Dr Efim Rabinovitch, managing director of PowerPrize in London, who says he was inspired to come up with his solution by an arson attack through a letterbox reported in the Evening Standard in May 2000 that killed four generations of one family.
His solution is to have a receiving box on the inside of the letter box aperture, but one which extends upwards from the aperture, instead of downwards. The flap on the letterbox aperture is hinged at the bottom instead of the top, which he says is the "Natural way to open it, without twisting your hand" and also one that makes it very difficult to introduce liquids. Should this be accomplished anyway, there is a slot immediately behind the letterplate opening that causes them to run out onto the feet of whoever is introducing them.
Letters inserted upwards fall behind the flap and are retained by a band so they do not fall onto the floor when the box on the back is opened to retrieve them. Nails on the back of the flap prevent letters being pulled out. The collecting box is sealed to the back of the door in a way that is not only watertight but able to withstand temperatures of up to 1400 deg C. This arrangement also prevents draughts and saves house energy.
Should one want to get a wardrobe or filing cabinet through the doorway, the box on the back can be lifted off.
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Coffee Time Challenge is just a bit of fun, but it is based on a real engineering solution. If you send in your ideas by using the
comment button below, we can add your solution as an alternative – perhaps something funny, practical, cheap or, of course,