Hydraulic rods have a wide range of applications in our lives, from small beds with storage functions, swivel chairs with lifting functions, large excavators, engineering cranes and forklifts, etc., will use hydraulic technology.
With the hydraulic bar, a lot of very laborious things will become very easy, such as a bed with storage function, if there is no hydraulic lever installed, then we need to spend a lot of effort to lift the bed board, and after installing the hydraulic lever, we only need to gently pull it, the hydraulic lever will easily lift the bed board. This is especially true in construction machinery, no matter how hard the soil and stone, excavators can be dug up by hydraulic technology. So the question is, even the hydraulic rod on the excavator does not look very thick and large, so why is this small hydraulic rod so powerful?
We can simplify the hydraulic rod as a piston filled with liquid, and to explain the principle of the hydraulic rod, we must first mention one person, that is, the French mathematician and physicist Blais Pascal, who proposed a law in 1653, that is, "Pascal's law".
Pascal's law, also known as the "principle of static pressure transfer", states that the pressure applied at any point in a closed liquid will be instantaneously transmitted throughout the various parts of the liquid, and the amount of pressure will not change. To put it more simply, if the resting state of the liquid does not change, then we apply a pressure in any part of the liquid, and the pressure at each point in the liquid will change by the same size. With this law in mind, Pascal invented the syringe, and yes, the syringe we use now for needles was invented by the physicist.
Because the pressure applied to the stationary liquid in a closed container is transmitted to each point at the same time, the liquid is squeezed out at the needle when we push the syringe.
In fact, the hydraulic lever is a syringe, and to easily push this syringe, we only need another small syringe. Suppose now we have a large syringe with a diameter of 4 cm and a small syringe with a diameter of 1 cm, and we connect the two syringes with a tube and fill them with liquid, and then we have someone push the big syringe and the small syringe respectively, so who can win? Of course it's the one that pushes the small syringe. Why? Because the pressure of the liquid is equal to the applied pressure divided by the force area, that is, in the case of the same applied force, the smaller the force area, the greater the pressure of the liquid.
The diameter of the small syringe is 1 cm, its force area is about 0.79 square centimeters, the diameter of the large syringe is 4 cm, its force area is about 12.56 square centimeters, that is to say, the force area of the large syringe is about 16 times that of the small syringe, so in the case of the same force applied, the pressure generated by the small syringe is 16 times that of the large syringe, so the small syringe can easily push the large syringe.
Now that we understand, we can think of the hydraulic rod as a mechanical system composed of two pistons of different thicknesses, and the small piston can give the large piston the power to destroy the decay with a light force. Knowing this, we only need a small syringe barrel to compete with a powerful hydraulic arm.
Let's do an interesting and not precise calculation.
Our most common use of hydraulic technology of large machinery is the excavator, how thick the hydraulic arm on the excavator, I am not sure, anyway, one hand can not hold, even if its diameter is 10 cm, then its force area is 78.5 square centimeters, and the general excavator stick excavation force is about 10,000 kg, so how much human thrust is? An adult pushing 100 kg should not be a problem, that is to say, the strength of the excavator is 100 times that of manpower, so we only need a small syringe with a force area of 1/100 of the excavator hydraulic arm to obtain the same force as the excavator, and a syringe diameter of 0.785 square centimeters is about 1 centimeter, so we only need a small syringe with a diameter of 1 cm to play a tie with the excavator.
Of course, this is only theoretical, in fact, the strength of the syringe barrel is not enough, so it may explode during confrontation, and the explosion of the swivel chair hydraulic rod is the same reason, that is, the instantaneous pressure value exceeds the bearing capacity of the inner wall of the hydraulic rod.
So how can you avoid a hydraulic rod explosion? If it is a regular product produced by a regular manufacturer, in theory, the strength of the material should be stress tested, generally there is no problem, but the problem is that many people cannot be sure whether their chair is a qualified product, so what to do? Manually install an explosion-proof steel plate, I installed a hydraulic rod under the swivel chair, a small steel plate 30 cm square, priced at 300 yuan, known as bullets can not penetrate. We use the example of "large and small syringe" just to illustrate the basic principle of hydraulic rods, in fact, the hydraulic rod in hydraulic machinery is not driven by a small syringe, on the one hand, because the strength of the small syringe is not enough, on the other hand, because the length of the small syringe is not enough, so in large hydraulic machinery are used to use a thing called "hydraulic pump" to play the role of small syringe.