Everyone is familiar with the concept of depreciation - it can be found in absolutely all areas of life, in particular in mechanical engineering. Depreciation is a process that allows you to absorb, extinguish part of the impact exerted by one body or force on another body. This principle is used everywhere: from mitigating the impact of traffic on a car to taking into account depreciation of equipment at the enterprise.
However, this article will not focus specifically on depreciation, but on such a thing as an absorbing device. If most people have heard about shock absorbers, then such devices for many may be new. The fact is that the absorbing device is a highly specialized device that is most often used on trains. In this area, this mechanism is very important, it is installed in all cars, but it can differ in types of absorption. This is what will be discussed in the article. What types of apparatuses are there and for what purposes can they be used in various cases?
What it is?
First of all, you should understand what an absorbing apparatus is and what it serves. So, this device is designed to repay or absorb (therefore it is called) part of the kinetic energy of the impact, thereby reducing the impact of various forces, including tensile and compressive, on the frame of the car where it is installed. How does an absorbing apparatus work? Resistance arises inside the device, which provides the conversion of kinetic force into other types of forces that do not harm the car. Therefore, the presence of such an apparatus in the car is not a matter of choice, but a prerequisite, otherwise the acting forces can lead to serious damage to the train, which will entail sad consequences. As for the types of absorbing apparatus, there are quite a large number of them, but not all of them are widespread. In this article, the main types and their action will be described in detail, as well as less popular types of devices.
Spring rejection
Nowadays, devices such as, for example, the RT-120 absorbing device, are common, however, it does not use springs, as it was at the very beginning. The device has the following specifications:
- Type of apparatus: friction.
- Maximum stroke: 120 millimeters.
- Maximum energy intensity: 90 kJ.
- Service life (before repair): 16 years.
- Total service life: 32 years.
Initially, such devices were exclusively spring, but over time they were replaced by useful and convenient, as well as much more functional and efficient devices. There were several problems, and the first of them was too much spring return. That is, they absorbed kinetic energy well, but at the same time gave it almost as much that leveled their usefulness. Secondly, in order for them to function correctly in cars, it was necessary to form products quite large, it can be said to be bulky, therefore they were abandoned. Low power consumption was a decisive factor, because other devices could be made no less efficient than spring ones, but at the same time much more compact. For this reason, at the moment, devices such as the RT-120 absorption device are used in cars, and spring models are used exclusively in buffer devices.
Spring Friction Apparatus
However, the fact that spring devices have not taken root in almost any area does not mean that such mechanisms have ceased to be used in this area. It’s just that they turned out to be not very effective, therefore spring-friction devices were created that transfer the main effect to frictional movements, while the springs have only an additional function, that is, they are responsible exclusively for potential and not kinetic energy. Let's see how it works. For example, an APE absorber takes on kinetic energy, which is generated by the collision of two cars. To begin with, the technical characteristics of this device should be indicated:
- The mass of the device: no more than 165 kilograms.
- Constructive stroke of the device: 90 millimeters.
- Rated power consumption: 110 KJ.
- Maximum energy intensity: 130 KJ.
- Initial tightening force: 230 kN.
- Closing force static: 1600 kN.
- Total service life: 32 years.
- Service life before repair: 16 years.
After a blow is made, the output does not have the recoil energy of the springs, but the kinetic friction force (i.e. friction) and the potential energy of deformation of the springs. This result turned out to be more than satisfactory for the depreciation of cars, therefore, such devices are widely used.
Now everywhere you can find the 73ZW absorber and other similar models. Technical characteristics of the device are as follows:
- The mass of the device: 214 kg.
- Constructive stroke of the apparatus: 90 mm.
- Operating temperature range: from + 50 ° to -60 ° .
- Dimensions: length - 625 mm, width - 318 mm, height - 230 mm.
- Initial tightening force: 200 kN.
- The closing force of the apparatus: 1600 kN.
Advantages of spring-friction devices
Spring-friction devices have been installed on cars for a very long time and are still in use today. Other types of devices exist, however, this type is one of the most common. There are several reasons for this. The first is simplicity. Secondly, the installation of absorbing devices of this type is a fairly simple and convenient process. Their dimensions are much smaller than that of spring devices, so the absorbing devices of freight cars are easily installed and do not cause difficulties in further maintenance. In addition, of course, it is necessary to note the variability and elementary design of these devices.
Hydraulic apparatus
Classes of absorbing devices are very diverse, and among them one can distinguish another very popular type. Hydraulic apparatuses in the manner of action are significantly different from spring-friction ones, since they take as a basis a fluid that provides maximum shock absorption. The apparatus has throttle openings calibrated accordingly. The strokes serve to ensure that shock absorbing fluid flows through them. These holes connect two cavities, which, depending on the load, are filled through these through passages. As a result, a uniform elastic resistance is created, which works effectively even with fairly powerful shocks.
Initially, there was one small problem, which was that the liquid could not quickly return to its original position, therefore, such a device led to missed shocks, that is, to those moments when the liquid from one cavity did not have time to flow into another in order to mitigate the shock of the car . That is why over time, inert gas began to be used in hydraulic apparatuses to ensure maximum elastic resistance. Repair of absorbing devices of this type is a little more complicated and expensive, but their use is an efficient and convenient process. A device is considered malfunctioning if fluid leakage, a change in stroke, or significant wear is detected.
How does depreciation occur in hydraulic units?
If we consider the hydraulic absorbing device of the car, then it is worthwhile to dwell in more detail on the principle of operation of this device. How can water soften the blow? The answer to this question is given by physics, because the density and viscosity of water provides the repayment and absorption of the kinetic energy of the shock, which is lost in the process of passing through the liquid, at the time of its overcoming and pushing into the neighboring cavity through special holes. Thus, the absorbing device of the automatic coupler, carriage and any other element can be hydraulic, because it is also not too complicated. The use of inert gas in this case is not mandatory. But thanks to this substance, the resistance of the liquid increases several times, and its return to its original state accelerates to take on another blow.
Energy intensity of the device
If an absorbing apparatus is considered, then one of its most important parameters is energy intensity, and it is on it that you should pay attention in the first place. This parameter represents the amount of kinetic energy that the apparatus is able to absorb before the shock absorbing elements are completely compressed, that is, until the moment when the device can no longer absorb shock. Accordingly, the larger this figure, the better. Springs have an extremely low energy intensity, and that is why they are not used on large cars, where the force of impact very quickly compresses the spring, which absorbs too little energy. It is also worth paying attention to the fact that the devices are created in such a way that kinetic energy is not completely absorbed - the necessary amount of energy should remain, capable of returning the device to its initial position. That is why inert gas is used in hydraulic devices, because thanks to it, not so much kinetic energy is required to return the liquid to its original position.
Other types of devices
The types of absorbing devices described above are not the only ones - there are much more of them, but, as was said at the beginning of the article, only the most popular ones will be described here. So, it is definitely worth noting the elastomeric absorbing apparatus, which is also very popular in various fields, including when installed in cars. This type almost exactly copies the described hydraulic units, but the main difference is that instead of ordinary water that is throttled through calibrated holes, these units use a special elastomeric liquid with a much higher viscosity, which increases its energy consumption, but at the same time makes it difficult service and also increases the cost. Also, frictional devices, which are considered devices of elastic elements, cannot be ignored. In them, the absorption of kinetic energy is due to the deformation of the elements due to their friction. You already met superficially with this type when you read about devices such as spring-friction devices.
Combined devices
Separately, it is worth telling about combined devices, one example of which is practically the most common type - spring-friction. Simply put, to combined devices are those that combine various types of depreciation. In this case, these are spring and friction types. Combinations can be varied. As indicated in the article, the combination of the action of springs and friction elements gave more than a positive result. It is this combined type of apparatus that is by far the most famous. In this field of activity, not all types of combination of two types of absorbing apparatus are allowed. The simplest example is the combination of elastomeric and hydraulic devices, since they are designed similarly and differ mainly in the liquid that is used in their maintenance.
Device selection
Which device must be chosen to achieve this goal? First of all, attention is drawn to the main parameter of absorbing devices - their energy intensity. It makes no sense to install a device with a high energy intensity on cars or other objects with a low kinetic impact force, since high costs will be observed without increasing productivity. Also, in no case can you put devices with low energy intensity on objects that are subjected to severe shocks, since the device’s energy will simply not be enough to absorb the desired amount of energy, and the shocks will be much stronger than is permissible in accordance with established standards.
Of course, there are other parameters that you should pay attention to, for example stability, that is, the number of successfully shock-absorbed shocks in relation to their total number, or the value of irreversibly outgoing energy, which is completely amortized by the absorbing device and is not used in the future to return it to its original position. These parameters are considered individually for each project, agreed upon before choosing a specific type of absorbing apparatus, in accordance with all established norms and requirements.