South Africa: When people hear the words "Jaws of Life," it is never associated with anything pleasant. That is because these lifesaving tools are mainly used to help people escape from horrific situations, such as terrible car crashes.
It is also an image we see in movies time and time again. A car veers off the road into another car, and one of the people inside gets trapped. Then help arrives, and they use a machine that looks like giant scissors to help cut the people out.
While we may think we know what the jaws of life are, very few people understand how they actually work.
Though many people believe that the jaws are life are tools regulated to fireman and police, they are actually a brand of tools that were trademarked by the Hurst Jaws of Life company.
The particular set of rescue tools that most people are familiar with are different types of piston-rod hydraulics also known as cutters, spreaders, and rams. These are what rescue teams use to cut open vehicles that have someone trapped inside. They can also help in removing people from collapsed concrete and steel buildings after earthquakes.
Like most hydraulic machines, the jaws of life are based on the concept of transmission forces from one point to another through a fluid. While most hydraulics utilize oil and the incompressible fluid, the jaws of life use a phosphate-ester fluid.
This particular fluid is fire resistant and electrically non-conductive. That is what makes this a more desirable synthetic fluid over oil.
Hydraulic systems work like this: a piston pushes down on the fluid, then the fluid puts force on the other piston, which is forced up. The Jaws of Life are considered to be unsophisticated, meaning that the tool does not require a lot of parts to make it work.
A valve switch controls which port the fluid is going to enter, then it forces the rod up and opens the arms of the spreader or the blades of the cutter. Then the switch is toggled again in order to retract the rod, which closes the arms or blades.
The two types of Jaws of Life machines people are most familiar with are spreaders and cutters:
The spreader is used to force pieces of a structure to spread apart. It can also be inserted into the side of a car in order to tear off that piece.
To get a spreader to work, a rescue worker needs to slide a valve switch that causes the fluid to flow from one hose into the cylinder, which then pushes up the pistons and rods. The rod is attached to linkages, which in turn are attached to the arms of the spreader.
When the rod goes up, it makes the linkages to rotate and open the arms. To close the arms, the rescue worker moves the valve in the opposite direction.
Like its name suggests, a cutter is used to cut through a vehicle, just like how a bolt cutter cuts through bolts. Cutters work in a similar fashion to spreaders, but instead of arms, they have claw-like extensions that are forged with heat-treated steel blades.
Though you have probably seen the Jaws of Life used many times in movies and television shows, you probably were not too familiar with how they worked. It is simply amazing how something that is considered unsophisticated can save so many lives.
But luckily, through the use of spreaders and cutters, many people have escaped dire situations and have lived to see another day.
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