Two triangular flat magnets in opposing directions (the point on the first opposite the base of the other) pull each other, one is flat on the floor, the other the bottom of the door portruding inward. When the door is left open it is slowly pulled back by the magnets. As the door closes the strength of the pull grows finally closing the door.
On the doorpost and the door lip another magnet silently pulls it and keeps it shut. (That part is an old invention, not mine).
The shape of the thinning triangles may be spiralling and the door magnet may fold up onto the door as the door closes.-- pashute, Nov 09 2020 Designer N S arranged magnets http://www.polymagnet.com/polymagnets/Spring capability is a feature [wjt, Nov 14 2020] Conventional door closers - the hydraulic damped sort used on fire doors - ate designed not to "slam". The last part of the travel is slow.
How does this magnetic system achieve that ?
(Not being snarky, genuine question - how about extra "buffer " magnets near the closure position ? )-- 8th of 7, Nov 09 2020 The inherent "slam" is to keep everyone awake thus assuring mental alertness, shirley?-- whatrock, Nov 09 2020 How do people wearing metallic items, like, say, steel-toed boots, avoid stumbling as the magnet attracts their footwear?-- RayfordSteele, Nov 09 2020 They don't ...
<Evil chuckle/>
Look on the bright side, at least if you get a user equipped with Rosa Klebb-style weaponised footwear, it'll slow them up a bit ... of course, the innocent will suffer too, but you can write that down to the cost of "security" ...-- 8th of 7, Nov 09 2020 Since when do people step on the 10 cm circle near the hinges side of the door?-- pashute, Nov 19 2020 ohh polymagnets! Thanks wjt! looking for an idea of yours so I can [+]-- pashute, Nov 19 2020 // Since when do people step on the 10 cm circle near the hinges side of the door? //
Whenever they suspect that said door might be booby-trapped, and wish to inspect it closely from numerous angles before risking opening it ?-- 8th of 7, Nov 19 2020 random, halfbakery