Lotspost - what is it? Operating principle. Application

Mechanization of lifting operations has always been a priority. In connection with this, an adaptation has long been invented, which has contributed to a significant reduction in the physical labor of workers involved in carrying out operations to lift or lower various objects. The name of this device is a chain block. What this is, we will consider in this article.

History of creation and definition

Nobody really knows when exactly the mechanisms for moving in the space of weights appeared and began to be used. First of all, we should note: the block block (what is it, technical literature can also suggest) is a system of blocks and ropes that makes it possible to significantly simplify and speed up the planned work with heavy objects.

The study of architectural monuments such as the pyramids of Cheops in Egypt, the Great Wall of China and other ancient structures unequivocally confirms that the pulley blocks, whose purpose and device will be considered below, were invented several thousand years ago. It is quite obvious that initially they were characterized by primitiveness.

general information

Let's try as much as possible to study the block. What is this from a technical point of view? In its essence, it is a group of blocks assembled into special clips, through which either a chain or a rope passes. The simplest pulley block is one block with a traction element stretched through it. This version of the scheme allows you to halve the thrust force required to move the load.

Classification

The pulley blocks are divided into two large groups: power and speed. Often, in practice, power analogs are used, which significantly reduce the tension of the cable. By the way, this effort can be calculated quite simply. To do this, you need to divide the weight of the load into the available multiplicity of the chain block. The question arises: what is multiplicity? Answer: multiplicity is the ratio of the number of branches of the organ on which the load is located to the numerical value of the branches that are already wound on the drum. Such a definition is applicable to force pulleys. As for high-speed pulley blocks, here the multiplicity is the value obtained from dividing the speed of the leading end of the rope by the speed of the slave.

In high-speed pulley blocks, the working force is applied to the mobile cage, the load, in turn, is fixed to the free end of the cable. The advantage in speed during the operation of this type of block is due to the increase in the lifting distance of the object.

Changing the multiplicity

The pulley blocks (the purpose and design of them for the years of existence basically remained unchanged) allow the introduction or removal of additional blocks from the system. Due to this, the required multiplicity is obtained. If the multiplicity is even, then the free end of the rope is fixed on the stationary structural element. If the multiplicity is odd, then the same end is attached to the cage with the hook.

In force pulley blocks, the increase in the number of folds makes it possible to reduce the diameter of the rope and, correspondingly, the dimensions of the drum and blocks. All this eventually leads to a reduction in the total weight of the entire system, a reduction in the gear ratio. But at the same time, a long rope will be required.

Division by number of branches

The pulley block (what you are now, obviously, you already understand) can be single or double, depending on the number of branches. In the first case, the flexible element moves along the axis of the drum. This option has a disadvantage, which consists in undesirable changes in the load on the drum supports, and in the absence of free blocks (that is, the rope from the suspension is immediately wound onto the drum), the object will move not only vertically, but also horizontally.

The double chain block provides fastening of both ends of a rope on a drum. An example is a chain hoist for a winch. In order to exclude the skewing of the hook suspension, equalizing blocks or balancers are used. Most often, such a system is operated in gantry or bridge cranes or heavy tower cranes.

Features

Absolutely any pulley block, the principle of which is generally similar to the operation of the lever, is good in that it does not require any special skills from the user, but obliges to be extremely cautious, as, like any other lifting mechanism, it is fraught with danger and is capable of injuring . In addition, the operation of pulleys shows that the traction elements used in their systems do not have ideal flexibility and are given some rigidity. That is why the oncoming branch of the rope is not able to instantly lie in the creek of the block or drum, and the running branch can not immediately straighten. This is best seen when using steel ropes.

Rules for pulleys

Each tackle is manual Works on the basis of the laws of physics, and therefore its functioning corresponds to a few fairly simple rules, with which it is desirable to read.

• Rule number one. The gain in the force is provided by extremely moving blocks or rollers, which are fixed on the load or the rope coming from the load. Stationary winning units in power never provide.
• Rule number two. The victory in the force is a multiple of the loss in the distance. In other words, for example, a two-fold tackle block For each meter of lifting the object requires pulling through its entire system two meters of rope. At the same time, the 6: 1 pulley requires that you pull out 6 meters of the cable to move up the load by one meter. Let's summarize: the greater the "strength" of the pulley, the slower (the same) the load will go up.

A complex block deserves special attention. In itself, it represents a collection of simple pulley blocks, each of which pulls the other. Thus, several pulleys can be mounted among themselves. This variety is most often used at the time of rescue operations.

In conclusion, it will be correct to say the following: a chain block (the principle of its operation is quite easy to understand by careful examination of the issue) has been, and will most likely remain for a very long time a faithful human assistant in solving a number of pressing issues related to construction, installation, Unloading and other operations, which are quite laborious. The main problem, the elimination of which is completely impossible for today due to again perfectly working physical laws, is the presence of frictional force in the system.