How about a water bed witch instead of "interfacing" with the person via a continous material uses a zillion small pistons for this purpose? The idea is that the continous material, elastic as it may be, is not able to follow all the points on your body's contour. What's more, pressure adjustments are very limited - which would not be the case with the zillions of pistons solution. The system would obviously benefit from some sort of built-in automation because most of the pistons (the ones you're not on) would be pushed up so there should be a system which could tell what's the minimal non-zero push applied on any given piston and adjust the pressure according to the current pressure setting.

The final idea is that mathematically every point in your body which is in contact with the bed would be pushed upwards with exactly the same force (in the pistons resolution range, that is).

You're wondering how many pistons? Well, if we have 1 piston per mm sq, we'd end up with 4 million pistons for a king-size bed (2x2m). Hey, I didn't say you should buy one of these - I say build one of these, sell it to Bill Gates for two million bucks and give me $100,000! (Yes, I know, it would have to be powered by Windows, but isn't it worth it?)
-- gutza, Feb 18 2002

Electromagnet Mattress http://www.halfbake...romagnet_20Mattress
Sounds a bit like this. [sirrobin, Feb 18 2002, last modified Oct 17 2004]

Nice idea. I think instead of providing equal force all over, this would be better if you could identify different areas of the body (based on location/shape/depression) and support them appropriately. Controlling the pistons would be tricky but not impossible. You could vary the density of them over different parts of the bed.
-- pottedstu, Feb 18 2002


'water bed witch'?? You have a good concept here but I think it's over complicated. You would achieve the same effect by dividing the waterbed into many small cells, the greater the complexity, the better the structure can react to distribution of weight. Adding in pistons is just an unnecessary engineering step, and we all know that unnecessary engineering steps are the surest way to provide weaknesses that will break down. Why computer controlled? Newton's 3rd deals perfectly with it.
-- sappho, Feb 18 2002


rods, sappho: The problem with existing beds is that, while they apply pressure to the lowermost parts of the body (hips and shoulder if you're lying on your side), the rest of your body is unsupported. I think pistons or something similar would be needed to provide an upward force in between these, to allow your weight to be spread more evenly. A waterbed does mold to some extent to your body, but is as much governed by the rigidity of the cover tending to a flat surface, as by its tendency to press up against you. And Rods: a board doesn't push at all against most of your body, so the force can hardly be equally spread.
-- pottedstu, Feb 18 2002


The pistons are still an alarming idea. Brownout! Power surge! Through the window!

Back to the waterbed: if the problem is the flat cover, make the cover not flat: give it squillions of fingers, like villi. Each can frely react to the weight above it, and because the water is all connected at the bottom of the mattress the pressure will equalize.
-- hello_c, Feb 18 2002


If you want all parts of the person's body to be pushed up with equal pressure, use a slightly-underinflated air mattress. Personally, I'd rather have something that applied more support to the parts of my body that were physically lower, but to each his own taste.

If you want something that's closer to what you describe than a waterbed, but not as all-the-way-there as an air mattress, perhaps you could use a waterbed filled with a lightweight oil. I know that gel-beds exist, but I think the gel is about the same density as water; a lower-density gel would allow the person to sink in more and be more widely supported.
-- supercat, Feb 18 2002


Ahhh. My bad (bed?) - I didn't explain the matter thoroughly - didn't want to be over-explanatory.

All of the pistons are connected to a common water tank. What we achieve is the same as a water bed, without the limitations of the material constraining the water into a bed. Now, a small child would need less pressure in the tank than a grown up. Therefore, all of the pistons have microswitches (no need for tension measurement) at both ends (fullly expanded/fully contracted). A computer - generic term here - processes all of the data in real time. Another big piston in the water tank is controlled by this computer, acted upon by a motor and the computer makes sure that at any given time there is at least one piston fully compressed. This ensures that the person(s) sitting on the bed cover the whole possible range of upward thrust the water bed is capable of (longer piston range, better vertical resolution).

Hope this answers most of the queries.
-- gutza, Feb 19 2002



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