Pivoting device for various equipment

In the modern world, special attention is paid to the creation and subsequent operation of various mechanisms and machines. Against the backdrop of this achievement, the current engineers are allowed to use already advanced developments, which at first glance do not seem to be anything supernatural, but at the same time perfectly show themselves in practice. One of such types of equipment, which is used today more and more often, will be discussed in this article. The name of this industrial product is the supporting and rotary devices (OPU). About all its features, varieties, repairs and scope of use, we'll talk in more detail.

brief information

So, the support-rotary device is a thought-out, highly efficient mechanism designed to transfer the load from the rotary part to the directly running element. These devices are not developed today, but over the years the popularity of this unit is growing, and it is installed not only on truck cranes and industrial units, but even on satellite antennas.

Classification

The pivot device, like any other factory technical product, has its own classification. Thus, each of these devices can rotate relative to:

• Static, fixed brackets.
• Fixed column.
• A stationary support circle.

Kinds

Ball-type ball bearings are produced in the form of a double row angular contact ball bearing. This device includes an outer and inner cages and two rows of balls between them. The outer casing is fixed to the swing frame with bolts and includes the upper and lower ring. The rings are centered by means of a collar. There is also an adjusting gasket.

Roller OPU has an undeniable advantage in comparison with the ball analog, which consists in a much higher load capacity. Roller bearing and rotary mechanism consists of:

• Rings of the inner.
• Running frame.
• Two rings.
• Roller.

The inner ring is meshed with the output gear of the swing mechanism due to its gear ring. The rollers are located between the rings and are perpendicular to each other. Rollers moving along the tracks absorb the loads that act down, and rollers on the tracks perform gripping functions, protecting the frame from spontaneous tipping. Lubrication of rollers takes place with the help of special greasers located in the ring.

Use in automotive engineering

Let's consider in detail the support-rotary device of the truck crane. This mechanism is able to take loads from the weight of the turning part of the crane and the weight of the lowered / lifted load. Also, the OPU is able to withstand the strong impact of wind load and various dynamic forces.

More often than not, the supporting and turning device of the truck crane is represented as a circle of skating or balls. Such a node is used on such cranes as AK-5G, AK-5, K-32 and is a circle of riding in combination with roller-type support elements. The circle is fixed at the top of the static frame, and the moving parts (supporting and roller elements) are at the bottom of the rotating platform of the machine.

Circle of skating

What is this product? In fact, this is a huge ring, cast from steel together with the central hub. The outer side of the circle has a special annular groove with a pair of inclined working tracks, on which the tapered rollers of support elements are supported. At the top of the circle is mounted a toothed crown of the mechanism providing rotation, and to the lower edge of the hub a static frame reducer is attached.

Beginning in 1960, automobile cranes began to be equipped with supporting-turning devices on balls, and the use of the circle stopped almost completely. The new SDAs are special and consist of:

• Internal rotation mechanism.
• Fixed clips.
• Pairs of outer movable rings (lower and upper), which are connected together by bolts.

Between the clips are arranged in two rows of balls of steel, whose diameter is 30 mm. The distinction between the balls occurs with the help of a special separator. Between the balls and clips there is a gap adjustable by the gasket.

Technical Activities

Support and rotary devices are rotary mechanisms that oblige them to pay close attention to the repair and maintenance personnel.

Each such support should be subject to periodic, thorough visual inspection. Also, you should always check the tightening of the connecting bolts, lubricate the rubbing parts in the inner cavity of the support and teeth.

For the first time, the tightness of the bolts is checked immediately before the unit is put into operation, and the next tightening is carried out in two to three work shifts. Important: the tightening of bolts must be carried out diagonally, in order to avoid distortion, which can lead to premature failure of the mechanism.

Operational safety measures

The pivoting device can be repaired or serviced not only within a variety of repair shops or other diagnostic centers, but also in the field by means of special mobile stations. To safely perform the full amount of work, it is necessary to follow the "Rules of labor protection in road transport" and other normative technical documents.

Engineers and fitters-repairmen have the right to perform any technical actions only if they have the appropriate qualifications, documented.

Before starting the maintenance, it is necessary to lock the machine still and completely eliminate the possibility of its spontaneous movement in any direction. Also, disconnect hydraulic, pneumatic, electrical systems and engine, if necessary, post warning posters.

A few words about excavators

The support-turning device of the excavator allows performing the functions assigned to it. The rotary platform itself rotates about a vertically oriented axis in both directions for an entire 360 degrees.

The support-turning device of the excavator can be of the following types:

• Single-roller.
• Two-roll.
• Double-row ball-bearing.

The most widespread in our time have already ball (roller) OPU. The undeniable advantage of such mechanisms is the lack of the requirement for their centering with a trunnion, which is necessarily installed on roller devices to compensate for horizontal forces.

The turning of the platform occurs due to the engagement of the cantilever gear and the ring gear. Gear in the process of the excavator moves along the crown, which in the end provides the turn of the platform to the desired angle. Gear engagement can be either external or internal.

It is also worth noting that the support-pivoting device allows the excavator to work normally on various rounds, without causing the machine's rotor to jam in the trench, and during the swivel movements of the excavator along with the semi-trailed working unit in the transport position.

Katkovo type devices have one significant drawback: the presence of mandatory gaps between the rollers and the turntable leads to the fact that during the operation of the excavator the platform begins to "chat".

Tower cranes

The bearing-turning device of the tower crane deserves special attention. The OPUs on the cranes of this type have the following varieties:

• The bell, which is put on the top of the stationary tower.
• The bell hung on the footplate.
• The shank, which rests on the intermediate, auxiliary thrust bearing and bearing held downwards.
• Circle ball and roller.

It should be understood that all these devices must be manufactured with high accuracy, in order to avoid later large distortions of the entire structure and misalignment of the surfaces, since these shortcomings are practically impossible to eliminate by any adjustment, and this, in turn, leads to jamming. In order to exclude inaccuracies, the swivel bell is made with hinged links, which eliminates additional loads in case of distortions.

As for roller-type rotary-type devices used in wheeled and crawler loaders, they are absolutely inapplicable in tower cranes, because here it is required to provide the highest accuracy. Otherwise, the resulting gaps will cause a very strong swing of the tower, and this already poses a threat to the safety of personnel.

In turn, ball and roller support wheels are completely free of this shortcoming. The rings of these circles are produced from high-quality steel, and the raceways of the rolling bodies are subjected to quenching. It is the minimum wear of these tracks that guarantees the minimum degree of swing of the pivoting towers that are supported by these circles. In addition, these supporting and turning circles do not oblige them to perform their adjustment in the course of work, which, of course, is their undeniable merit.

Precision manufacturing of rings and the use of rolling elements, whose dimensions fluctuate within microns, makes it possible to reduce the magnitude of the axial and radial clearances.

Also, in order for the crane to be fully operational, it is necessary to reduce the compliance of the running frame of the unit. The deflection of the frame should not be more than half the axial clearance, which is measured in the support circle. The upper frame of the rotating platform must also have high rigidity, so that the loads that act on it, evenly distributed throughout the length of the circle. However, at the same time, the deformation of the upper frame should exceed the analogous index of the lower frame, otherwise a very undesirable phenomenon may occur-an accidental jamming of the lower row of rollers.

Industry

The pivot arm of the manipulator, used, for example, in metallurgy or the chemical industry, is very similar to the construction of a truck crane. Also there are a gear ring and a gear, a frame, a load-lifting element. In most manipulators operated in the same blast furnaces or rolling mills, a hydraulic drive is used in which non-combustible emulsion types are used as a working fluid.

Satellite TV and communication

The antenna support and swiveling device serves to suspend the antenna system itself, as well as to guide the beam radiated by it onto the retranslating satellite. The OPUs of the antennas are divided according to the scheme of fixing the mirror. The polar suspension is very popular, which allows you to rotate the antenna in one plane while still viewing the visible part of the geostationary orbit.

The suspension itself is moved by the operation of an electric drive, which ensures the rotation of the antenna.

In general, the drive of the pivoting device functions in rather aggressive and difficult conditions: there are large temperature changes, wind loads, and atmospheric precipitation. The linear drive of the support-rotary devices is equipped with a low-power electric motor, which in case of overheating is turned off by the operation of a special sensor - bimetallic platinum.

If we are talking about the type of horizontals-horizons, it is appropriate to point out that in this case the device is equipped with a gear mechanism that rotates the antenna along the horizon around the polar axis along the entire length of the geostationary orbit.

Creature

The production of support-rotary devices is a rather complicated and labor-intensive technological process. It obliges employees of enterprises to have appropriate skills and high qualifications.

The manufacture of the support-rotary devices takes place in strict accordance with the required temperature conditions. So, in particular, the basis of these products are blanks of alloyed, normalized rolled products, which has passed all the stages of heat-strengthening. Reliability and longevity of the OPU is provided by the use of special hardening inductors.

Service

As you yourself have probably realized, repairing the pivot-turning device is an inevitable exercise that should be trusted by professionals.

When rolling bearings are used in the OPU, a so-called point contact occurs between all the balls and raceways. Because of this, along the perimeter of these tracks there are annular grooves of a spherical shape. All this leads to the failure of the device and the need to carry out repair operations.

This problem is eliminated as follows. Initially remove the resulting grooves from the treadmills by boring, and then perform hardening of the contact surface finish-plasma treatment. After that, to increase the longevity of the circles of the supporting and rotating devices in the tracks, the roller rolling bodies are combined in a crosswise manner, combined with the ball "brothers". This position of the rolling elements ensures the elimination of defects from the rollers by the spherical surface of the ball body.

Practice has shown that the most loaded part of the OPU is the lower movable ring, which, in turn, has different strengths across its entire section. For example, the ring under the bodies of rolling on the scale HRC has a hardness index of 60 units, and the bottom surface - 35 units. It is because of this at the peak load that destruction begins to occur from the lower surface, and this eventually causes deformation of the supporting and turning circle and a decrease in its reliability and durability.

On the basis of the foregoing, it becomes clear that during the repair of the OPU, particular attention is paid to the lower movable ring, which is connected to a gasket of a special high-strength material. It is allowed to use a sectional gasket, joints of which can be located in unloaded or lightly loaded zones. Fastening of the auxiliary gasket takes place with the help of screws or industrial types of glue.