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Summary
DescriptionWater gun principle.svg
Comparison of simple (A), air pressurised reservoir (B), air separate pressure chamber (C) and Constant Pressure System (D) water guns based on http://kknews.cc/news/z6ag9jq.html redrawn by CMG Lee.
In (A), pushing the trigger (1) expels the cylinder's contents through the nozzle; releasing it refills it from the reservoir (2).
In (B), pumping the piston (3) forces air into the reservoir (4), increasing its pressure; opening the valve (5) expels the reservoir's contents.
In (C), pulling out the piston (6) draws in water from the unpressurised reservoir (7), whereas pushing it in pressurises the firing chamber (8); triggering the valve (9) expels the chamber's contents.
In (D), the firing chamber is replaced with an elastic bladder (8a).
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