Just about every kid has had or still has a water blaster. Sure most of us had water guns that barely got anything wet, but kids today have monstrous water blasters that will literally soak their target. How do these work?
On the old-style water guns, a trigger lever activates a small pump. The main moving element in this pump is a piston housed inside a cylinder. There is also a small spring inside the cylinder. The operation of the pump is very simple, pulling the trigger back pushes the piston into the cylinder, compressing the spring and causing the piston to be pushed back out of the cylinder when the trigger is released.
These two strokes of the piston are the entire pump cycle. The downstroke shrinks the volume of the cylinder, forcing the water out of the pump and the upstroke has the spring pushing the piston back out, expanding the cylinder volume and sucking water into the pump. This pump, attached to a plastic tube, draws water from the bottom of the reservoir usually located inside the gun.
The pump must only force water up, it cannot force water back into the reservoir. A one-way valve is needed for this and consists of a tiny rubber ball that rests neatly inside a small seal. The pump forces the water down a narrow barrel and out a small hole at the gun’s muzzle. The hole or nozzle focuses the flowing water into a concentrated stream.
Super Soakers, another type of water gun, is built around a pump mechanism that does not actually drive the water out of the gun. The pump on this water gun builds up water pressure before the blast. In the early days of these guns, this pressure was built by pumping air directly into a single water reservoir. In later models, water was pumped in instead of air. These guns did not produce a very powerful stream either.
Water blasters are water guns that contain two water reservoirs that are connected together with a network of tubes. To load the gun, the larger reservoir is filled with water. To prime the gun for a blast the pump handle is pulled in and out several times. The pump handle is connected to a long, narrow piston that moves back and forth inside a cylinder.
This pump is similar to the one in an original water gun and relies on the one-way valve system to control the direction of water flow. On the upstroke of the pump cycle, the pump handle is pulled out and the receding piston pulls in water from the large reservoir above. A one-way valve keeps water from flowing up from the smaller reservoir.
On the downstroke of the pump cycle, the pump handle is pushed in and the piston drives the water out of the cylinder, through the one-way valve and into the small reservoir. The purpose of this pump inside a Super Soaker is to compress air. Each time water is driven from the large reservoir into the small reservoir, it pushes up against all of the air insides. When more water is added to the small reservoir, it takes up a greater and great volume.
Due to a limited amount of space in the reservoir, these larger volumes of water compress the air inside the gun so that is has a much higher pressure than the air outside the gun. The cushion of high-pressure air pushes on all the water in the reservoir, the water presses on the sides of the gun, trying to get outside to restore pressure balance.
The trigger, which is simply a lever secured to the gun housing, is the only thing that keeps the water inside the gun. A stiff length of metal attached to the housing holds the top part of this lever against the flexible plastic tube leading to the gun’s barrel, pinching it so no water can get through. When pulling the trigger back, the metal piece bends, and the lever releases the plastic tube.
When the passageway is open, the pressurized air pushes all of the water out of the gun reestablishing pressure equilibrium with the air outside. If enough pressure is built up, the water is expelled at a very high velocity. Each bit of water further compresses the air cushion causing the force of the blast to depend on how much water is pumped into the small reservoir.
At a high-enough pressure level, the outward force of the compressed air and pressurized water might exceed the structural integrity of the plumbing in the gun, causing it to leak. The trigger mechanism is designed to let some water through when the pressure reaches a certain level to keep this from happening. The leak level is determined by the strength of the metal that holds the trigger down.
Essentially, this piece of metal is like an ordinary spring, and its springiness is determined by its composition. If the metal is more rigid, it will take a higher water pressure level to push it out of the way. A more flexible piece will let some water leak at a lower pressure.
A new wave of Super soakers now exists with higher-pressure levels that feature the constant pressure system. The main component in this system is a simple water bladder. This bladder is like a balloon made out of more rigid material.
The pumps in these soakers are similar to the other pumps in the earlier super soakers, but water and air are driven into the water bladder instead of into a plastic reservoir. As more water is pumped in, the bladder expands, very similar to the way a balloon expands as air is blown into it. When stretched, the bladder wants to return to its nature shape, so it applies a good deal of inward pressure on the water.
When the trigger is pulled and opens up the passageway to the gun barrel, the pressure drives all the water out of the gun allowing for more powerful water blasts.When the trigger