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I have an idea for a new kind of surge device.
I had hoped to see if it was patentable, but I finally realized I'll never get
around to it. So I offer it to the list, for whatever it's worth to
individuals. If you're honorable and if it's valuable, please don't use it for
commercial profit without my permission. End of spiel; I have no illusions as
to how "binding" this is.
I have prototyped it, and the basic idea seems to work, but my skills and tools
and materials are so primitive that I cannot really be sure how well it would
work in a real device. I don't know what mechanism the new "Silent Surge" unit
uses; perhaps this is it.
The key to this surge device is an auto-opening/closing valve, of my own design.
The valve can be used to control any size surge. I believe it will be quieter
than the Borneman or Carlson devices. Depending on the exact design, you can
control how strong a surge it generates (perhaps).
Here's a simplistic description:
The device starts with a tank holding the surge water. The valve is installed
at "the bottom" of one of the vertical walls. The valve leads to a pipe which
goes to the aquarium.
The valve consists of a rectangular piece of material. It is placed in a hole
in the wall, exactly the same size/shape. The valve pivots on an axis (axle?)
which is just below the horizontal centerline (i.e., this way: ---). There is a
"stop" which prevents the bottom edge from pivoting outwards. There is a weight
of some kind attached to the bottom half to make it heavier than the
slightly-larger-in-area top half.
Principle of operation:
As the tank fills, the water pressure on the inside of the bottom of the valve
flapper forces the valve to stay closed (pressed against the bottom stop).
Until the water level reaches the pivot line, it remains in this state.
The force the water applies to the valve at each point varies according to the
depth of the point. There is a point called the "center of pressure" about
which, vertically, the pressure is evenly distributed. If the pivot point were
actully on the midline, the valve would always remain closed, because there's
always more pressure on the bottom half than the top half, and therefore the
center of pressure is always below the pivot point. However, with a larger
upper "half" area, as the water level rises, eventually the center of pressure
will rise above the pivot point. When that happens, the valve opens (the top
half pivots outward). The depth of the water when this happens (and implicitly,
the volume of the surge) depends on how close the pivot point is to the actual
midline.
While the valve is open, and the surge water is running out, the construction of
the valve must have some design mechanism to keep it open for the duration of
the surge. Perhaps channel the water to flow over the now-horizontal valve. My
toilet flapper has an alternative device (a "drip box") which serves the same
purpose.
When all the water has run out, then the extra weight on the lower half causes
the valve to pivot closed, the incoming water pushes it closed, and the cycle
starts again.
Notes:
I believe the trick to making this be silent will be to have the outflow of the
surge tank, including the valve, actually be inside the aquarium. In this case,
the surge tank wouldn't be a simple shape. (And you have to account for the
force that the aquarium water applies to the other side of the valve.)
The opening/closing cycle depends only on the height of the water. You can have
any volume of surge by controlling the other dimensions of the surge tank.
Higher water depths will make a more powerful surge.
The rectangular shape of the valve was for simplicity's sake. You can have
other shapes, but the area calculations are different.
The relationship between the pivot point and the height of the water is
non-linear, so if the height is critical, the pivot point placement is very very
critical.
The exact construction of the valve is critical. It must seal reasonably tight
when closed, pivot open reliably (with a fail-safe overflow backup), stay open
thru the whole surge, and close when the surge is complete. I believe there are
a number of ways to do this; but all require good workmanship/tools, which I
don't have.
I have the formulas required to compute the height of the water and the pivot
point in an Excel spreadsheet (not well doc'd, though). Lemme know (off-list)
if you'd like to get it.
Have fun! If anyone actually makes one of these, I'd sure like to get one!
--Jon Balgley
jbalgley@home.com
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