The principle of operation of the hydraulic system of attachments. Hydraulic system How the hydraulic system works

The advantages of hydraulic systems over other methods of power transmission are:

Simplicity of design. In most cases, multiple hydraulic components in a bundle can replace more complex mechanical links.
Flexibility. Hydraulic components can be positioned with considerable flexibility. Pipes and hoses instead of mechanical elements almost completely eliminate problems in choosing a location.
smoothness. Hydraulic systems are smooth and quiet in operation. Vibrations are kept to a minimum.
Control. Control over a wide range of speeds and forces is fairly easy to implement.
Price. High performance With minimal losses on friction ensures the cost of power transmission at a minimum level.
Overload protection. Automatic valves protect the system from damage from overload.

The main disadvantage of a hydraulic system is keeping precision parts in good condition when they are exposed to bad weather conditions and pollution. Protection against rust, corrosion, dirt, oil, wear and other adverse conditions environment is very important condition. Below we consider several basic types of hydraulic systems.

Hydraulic jack

This system (Figure 1) consists of a reservoir with liquid, a system of valves and rods, and is a Pascal hydraulic lever. Moving the small rod (pump) down causes the large rod (lift cylinder) to be lifted up with a load. Since the pressure under the small and large rods is the same, but the areas of the rods (on which this pressure acts) are different, in accordance with Pascal's law, with a small force on the pump rod, a much greater force is achieved on the lifting cylinder.

Figure 1 shows the intake stroke at the top. High school graduation check valve closes under pressure under load, and the suction check valve opens so that liquid from the reservoir fills the pumping chamber. IN bottom diagram Figure 1 pump plunger moves down. The inlet check valve closes under pressure and opens the outlet valve. A mass of fluid is pumped under the large piston to raise it. To lower the load, a third valve (needle valve) is provided in the system. When it is opened, the volume of liquid under the large piston communicates with the reservoir. The load pushes the large lift rod down and forces the liquid back into the reservoir.

up- intake stroke and load holding, at the bottom- tact of release and lifting of the load.

Figure 1 - Hydraulic jack

Reversible hydraulic motor

Figures 2 and 3 show a mechanically driven hydraulic pump and a hydraulic reversible rotary motor. A flow direction valve (reversing valve) directs fluid flow either to one side or the other of the motor and back to the tank. Thus, the possibility of working hydraulic motor With different directions rotation (reversibility) The safety valve protects the system against overpressure and can create a bypass to exit the fluid flow from the pump back to the tank if the pressure rises too high.

Figure 2 - Reversible hydraulic motor

Figure 3 - Reversible hydraulic motor (continued)

Open Center System

In this system, the control directional control valve must be opened in the center to allow oil flow to pass through the valve and return to the reservoir. Figure 4 shows this system in the neutral position. In order to handle multiple hydraulic functions at the same time, an open center system must have correct connections which are discussed below. The open center system is effective for single hydraulic functions and is limited to multiple functions.

Figure 4 - Hydraulic system with an open center.

(1) Series connection. Figure 5 shows an open center system with hydraulic consumers/distributors connected in series. The oil flow from the pump is directed to three control valves in series. The center of each distributor is open in the neutral position to allow free flow of oil from the pump to the reservoir. The direction of oil flow is indicated by arrows. The flow from the outlet of the first valve is directed to the inlet of the second, and so on. When the control valve is operating, the incoming oil enters the cylinder, which is controlled by the corresponding control valve. The return fluid from the cylinder is directed through the return line and to the next valve.

Figure 5 - Open center hydraulic system with serial connection.

This system is only effective if one control valve is operating at the same time. When this happens, full oil flow and pump outlet pressure are available for this function. However, if more than one directional valve is in operation, the total amount of pressure and flow required for each function cannot exceed the system reset setting (reset valve setting).

2) Series-parallel connection. Figure 6 shows the change from a serial connection. Oil from the pump is directed through control valves in series as well as in parallel. Valves are sometimes "piled up" to provide additional flow passage. In the neutral position, fluid flows through the valves in sequence, as the arrows indicate. However, when either directional valve fires, the outlet on the operating valve is closed, but oil flow is made available to all other valves through a parallel connection.

Figure 6 - Open center hydraulic system with series-parallel connection.

When two or more valves operate at the same time, the cylinder that needs the least pressure will operate first, followed by the cylinder with the next lower pressure, and so on. This ability to operate two or more valves at the same time is an advantage over a series connection.

(3) Flow divider. Figure 7 shows an open center system with a flow divider. The flow divider receives the volume of oil from the pump and divides it between two functions. For example, the flow divider could be set to open the left side first in this case if both control valves were actuated at the same time. Or it can split the oil flow on both sides, equally or in different percentages. For such a split flow system, the pump must be powerful enough to control all functions at the same time. It must also supply liquid at maximum pressure to the most important of the hydraulic functions. And this means that a large number of horses are wasted when only one control valve is operating.

Figure 7 - Hydraulic system with open center and flow divider.

Closed center system

In this system, the pump can be idle (standby) when oil is not needed for the function to work. This means that the control valve (distributor) is closed in the center, stopping the flow of oil from the pump. Figure 8 shows schematically a closed center hydraulic system during the operation of the hydraulic function. In order for several functions to work simultaneously, the closed center hydraulic system has the following connections:

Figure 8 - Closed center hydraulic system.

(1) Pump with constant flowand battery. Figure 9 shows a closed center hydraulic system with an accumulator. This system has a small pump, but charges the battery at a constant volume. When the accumulator is charged to full pressure, the unloader valve diverts pump flow back to the reservoir. The check valve keeps oil under pressure in the circuit.

Figure 9 - Closed center hydraulic system with accumulator.

When the control valve is operated, the accumulator discharges its pressurized oil and drives the cylinder. As the pressure begins to drop, the unloader valve opens and directs the pump flow to the accumulator to recharge the flow. This system, using a small displacement pump, is effective when oil is needed only for a short period of time. However, when the hydraulic function needs a lot of oil for longer periods, an accumulator system may not be able to handle it unless the accumulator is very large.

(2) variable flow pump. Figure 10 shows a closed center hydraulic system with a variable displacement pump with the control valve in neutral. When the control valve is in the neutral position (center closed), oil is pumped in until the pressure rises to the set level. The pressure regulating valve allows the pump to turn itself off and maintain that pressure in the valve. The pump is in standby mode. The oil flow of the pump is close to zero (self-leakage in the pump is replenished), the pressure is equal to the settings of the pump standby pressure valve.

When the control valve is actuated (moves up), oil is diverted from the pump to the bottom of the cylinder cavity. The pressure drop caused by the communication between the pump pressure line and the lower cylinder cavity brings the pump from standby to operating mode to create oil flow and pressure on the bottom of the piston to lift the load.

Figure 10 - Closed center hydraulic system with variable flow pump.

At this time, the upper cavity of the cylinder is connected to the return line, which allows the oil to be pushed out of the piston to return to the reservoir or pump. When the control valve returns to the neutral position, the oil becomes locked on both sides of the cylinder, and the pressure supply from the pump to the hydraulic cylinder is tightly blocked. After this sequence, the pump goes back into standby mode. Moving the spool to the down position directs oil to the top of the piston cavity and causes the weight to move down. The oil from the bottom of the piston is sent to the return line to the reservoir.

Figure 11 shows the same closed center system, but with a booster pump (charging pump) that pumps oil from a reservoir to a variable flow pump. During operation of the charge pump, the necessary pressure is created for the main pump and required amount oils for it. All this makes the operation of the variable flow pump more efficient. The oil return from the operating hydraulic functions of the entire hydraulic system is directed directly to the inlet of the variable flow pump.

Figure 11 - Closed center hydraulic system with booster pump.

As modern machines need more hydraulic power, the closed center hydraulic system is more advantageous. For example, on a tractor, oil may be required for power steering, brake booster, slave cylinders, three-point hitch, loader and other attachments. In most cases, each function requires a different amount of oil. In closed center systems, the amount of oil for each function can be set by line or valve size or by throttling with less internal heat generation compared to using flow dividers in a comparable open center system. Other advantages of the closed center system are:

Does not require unloading valves, as the pump simply turns off by itself when the standby pressure is reached. This prevents heat build-up in systems where relief pressure is often reached.
Has lines, valves and cylinders that can be adapted to the flow requirements of each function.
Oil flow reserve for full work and hydraulic system speed, available at low engine speeds per minute (RPM). More functions can be active at the same time.

Greater performance in some cases. For example, hydraulic functions such as brakes that require force but very little piston movement. By holding the valve open, in standby mode, pressure is constantly applied to the brake piston without loss of efficiency as the pump returns to standby mode.

Hydraulic jack device and principle of operation is based on physical properties liquids that retain their volume during compression.

The hydraulic jack is a portable lifting device designed for heavy objects.

The purpose of the hydraulic jack

A hydraulic jack is a stationary, portable or mobile lifting device designed for heavy objects. It is used when performing repair and construction work and as part of cranes, presses, hoists.

Modern designs of hydraulic devices are used at the enterprises of the oil refining industry, facilities of the energy sector of the industry, in agriculture. High level productivity and efficiency index, ease of operation and maintenance allow the use of hydraulic jacks in the domestic sector.

This type of equipment is able to easily operate both in horizontal and vertical positions, which has found its application on sites for installation and construction work. The unit is used for tensioning reinforcing structures made of stressed concrete.

The structure of the hydraulic lifting device

The unit is set up as follows:

frame;
working fluid;
working piston.

The design of the device can have an elongated or short body, for the manufacture of which hardened special steel is used. The body of the device is assigned to perform several functions. It is a guide cylinder for the working piston and serves as a reservoir for storing the working fluid.

A screw with a lifting heel is capable of being screwed into the plunger using a special thread. By unscrewing it, you can change the maximum height of the jack heel. Hydraulic devices are equipped with working pumps having a manual, foot or air drive. The design provides for the installation of safety valves and some structural elements ensuring long and trouble-free operation of the lift.

The hydraulic pump and the cylinder with the piston are arranged in such a way that they provide the extension and lifting of the special platform. After the extension of the stem, return to initial position carried out using a bypass valve.

There are several different modifications of lifting hydraulic units, which have their own areas of application.

The most common are:

bottle type devices;
rolling type devices;
hydraulic jacks of hybrid design;
hook-type units;
diamond aggregates.

Various designs of hydraulic jacks have their own characteristics in the device, which are determined by the scope of the device.

Each of the types of hydraulic jacks is designed in its own way, however, the principle of operation is the same for all.

The principle of operation of the hydraulic jack is based on the use in the design of the apparatus of communicating vessels with a working fluid, the role of which is played by a special oil. Before use, the device must be placed on a flat, solid surface and the bypass valve closed. After installation and preparation of the unit, you can use it in operation.

The rod is lifted from the fifth by means of a pump that injects the working fluid into a special cylinder.

Due to the property of the liquid to resist compression with increasing pressure, the piston moves in the working cylinder. This leads to the movement of the rod with the lifting heel. The descent of the latter occurs by opening the bypass valve counterclockwise.

Pumping of working oil is carried out by a drive pump and a lever mounted on it. The oil moves from the pump to the working cylinder through special valve.

The return of liquid during the operation of the device is prevented by two valves: discharge and suction.

To install the lift in its original position, a special valve is provided in its design, when opened, the working fluid flows from the cylinder to the pump of the unit.

The presence of a screw under the working heel in the jack device allows you to expand the possibilities of using the device.

For lifting, a special heel is made of high-strength steel. The force of the hydraulic jack is regulated by a built-in pressure gauge.

Advantages and disadvantages of hydraulic jacks

The physical features of the liquid allow for a smooth lifting, lowering of the load and fixing it at a certain height. Hydraulic jacks provide high efficiency, which reaches 80%. The carrying capacity of the unit is due to the presence of a large gear ratio between the cross-sectional indicators of the pump and working cylinder, plunger.

It is necessary to regularly flush the hydraulic jack, as well as change the oil and pump it.

Hydraulic lifts have a number of disadvantages. First of all, it should be noted that any model of this equipment has a certain starting height for lifting the load, below which the device cannot be operated. The disadvantage of this equipment is also the inability to accurately adjust the height of the lowering. In order to ensure trouble-free operation of the device, it is recommended to constantly monitor the cleanliness, quality and level of oil in the jack reservoir. The normal operation of the device is ensured by the tightness of the valves and glands used in the design of the unit. Transportation and storage of the device is carried out exclusively in a vertical position, if this requirement is violated, the working fluid can flow out of the device reservoir.

One of the disadvantages is the slowness of the units in operation. The disadvantages also include the weight of the device, its large size and high cost. In addition, single-plunger devices have a small stroke of the working rod, which is another drawback.

Possible malfunctions in the operation of the hydraulic jack

In any case, hydraulic jacks require care and maintenance, which consists in adding oil to the working tank of the unit. In addition, after a certain period of operation, it is required to flush the fixture, change the oil and pump it. Oil from the working reservoir can leak through the seals and various seals used in the design of the device. In addition to leakage during operation of the device, malfunctions such as jamming during lifting and the impossibility of lowering the rod may occur.

To eliminate oil leakage during the operation of the device, seals and seals are replaced. For this purpose, specially designed repair kits are used. During the repair process, the unit is disassembled, the seals are replaced, the hydraulic jack is assembled, after which the working fluid is filled and pumped.

To eliminate jamming, the device is disassembled and its components are inspected for corrosion and contamination. If the first one is detected, special processing and the dirt is washed out.

The hydraulic system is a device designed to convert a small effort into a significant one using some kind of fluid to transfer energy. There are many types of nodes that operate according to this principle. The popularity of systems of this type is primarily due to their high efficiency, reliability and relative simplicity of design.

Scope of use

Widespread use of this type of system found:

In industry. Very often, hydraulics is an element of the design of metal-cutting machines, equipment designed for transporting products, loading / unloading them, etc.
In the aerospace industry. Similar systems are used in different kind controls and chassis.
In agriculture. It is through hydraulics that the attachments of tractors and bulldozers are usually controlled.
In the field of cargo transportation. Cars are often equipped with hydraulic
In the ship, in this case, it is used in steering, it is included in the design scheme of turbines.

Operating principle

Any hydraulic system works on the principle of a conventional liquid lever. The working medium supplied inside such a node (in most cases, oil) creates the same pressure at all its points. This means that by applying a small force on a small area, you can withstand a significant load on a large one.

Next, we consider the principle of operation of such a device using the example of such a node as a hydraulic structure. The design of the latter is quite simple. Its scheme includes several liquid-filled, and auxiliary). All these elements are connected to each other by tubes. When the driver presses the pedal, the piston in the master cylinder moves. As a result, the liquid begins to move through the tubes and enters the auxiliary cylinders located next to the wheels. After that, braking is activated.

Design of industrial systems

The hydraulic brake of a car - the design, as you can see, is quite simple. IN industrial machines and mechanisms, liquid devices are used more complicated. Their design may be different (depending on the scope of application). However, the circuit diagram of an industrial design hydraulic system is always the same. It usually includes the following elements:

Fluid reservoir with mouth and fan.
Coarse filter. This element is designed to remove various kinds of mechanical impurities from the liquid entering the system.
Pump.
Control system.
Working cylinder.
Two fine filters (on the supply and return lines).
Distribution valve. This structural element is designed to direct fluid to the cylinder or back to the tank.
Reverse and safety valve s.

Hydraulic System Operation industrial equipment also based on the principle of fluid leverage. Under the influence of gravity, the oil in such a system enters the pump. Then it goes to the control valve, and then to the piston of the cylinder, creating pressure. The pump in such systems is designed not to suck the liquid, but only to move its volume. That is, the pressure is not created as a result of its work, but under the load from the piston. Below is a schematic diagram of the hydraulic system.

Advantages and disadvantages of hydraulic systems

The advantages of nodes operating on this principle include:

The ability to move loads of large dimensions and weight with maximum accuracy.
Virtually unlimited speed range.
Smoothness of work.
Reliability and long term services. All components of such equipment can be easily protected from overloads by installing simple pressure relief valves.
Efficiency in work and the small sizes.

In addition to the advantages, hydraulic industrial systems, of course, and certain disadvantages. These include:

Increased risk of fire during operation. Most fluids used in hydraulic systems are flammable.
Sensitivity of equipment to contamination.
The possibility of oil leaks, and therefore the need to eliminate them.

Hydraulic system calculation

When designing similar devices many different factors are taken into account. These include, for example, the kinematic fluid, its density, the length of pipelines, rod diameters, etc.

The main goals of performing calculations for such a device as a hydraulic system are most often to determine:

Pump characteristics.
The magnitude of the stroke of the rods.
working pressure.
Hydraulic characteristics of highways, other elements and the entire system as a whole.

The hydraulic system is calculated using various kinds of arithmetic formulas. For example, pressure losses in pipelines are defined as follows:

The estimated length of the lines is divided by their diameter.
The product of the density of the liquid used and the square average speed stream is divided into two.
Multiply the obtained values.
Multiply the result by the path loss factor.

The formula itself looks like this:

∆p i \u003d λ x l i (p) : d x pV 2: 2.

In general, in this case, the calculation of losses in the mains is carried out approximately according to the same principle as in such simple designs like hydraulic heating systems. Other formulas are used to determine pump characteristics, piston stroke, etc.

Types of hydraulic systems

All such devices are divided into two main groups: open and closed type. The schematic diagram of the hydraulic system considered by us above belongs to the first variety. An open design is usually used for devices of low and medium power. In more complex systems closed type instead of a cylinder, a hydraulic motor is used. The liquid enters it from the pump, and then returns to the line again.

How is the repair done

Since the hydraulic system plays a significant role in machines and mechanisms, its maintenance is often entrusted to highly qualified specialists of companies engaged in this particular type of activity. Such firms usually provide a full range of services related to the repair of special equipment and hydraulics.

Of course, in the arsenal of these companies there is all the equipment necessary for the production of such work. Repairs to hydraulic systems are usually done on site. Before it is carried out, in most cases, various diagnostic measures must be taken. To do this, hydraulic service companies use special installations. The components necessary to fix problems are also usually brought by employees of such firms.

Pneumatic systems

In addition to hydraulic, pneumatic devices can be used to drive the nodes of various kinds of mechanisms. They work in much the same way. However, in this case, the energy of compressed air, not water, is converted into mechanical energy. Both hydraulic and pneumatic systems quite effectively cope with their task.

The advantage of devices of the second type is, first of all, the absence of the need to return the working fluid back to the compressor. The advantage of hydraulic systems in comparison with pneumatic ones is that the medium in them does not overheat and does not overcool, and therefore, no additional components and parts need to be included in the circuit.

Modern mechanisms, machines and machine tools, despite the seeming complex device, are a collection of so-called simple machines- levers, screws, gates and the like. The principle of operation of even very complex devices is based on the fundamental laws of nature, which are studied by the science of physics. Consider, as an example, the device and principle of operation of a hydraulic press.

What is a hydraulic press

A hydraulic press is a machine that generates a force that is much greater than that originally applied. The name "press" is rather arbitrary: such devices are often really used for compression or pressing. For example, to get vegetable oil oilseeds are strongly pressed, squeezing out the oil. In industry, hydraulic presses are used to manufacture products by stamping.

But the principle of the hydraulic press device can be used in other areas. The simplest example: a hydraulic jack is a mechanism that allows, with the application of a relatively small effort of human hands, to lift loads, the mass of which obviously exceeds the capabilities of a person. On the same principle - the use of hydraulic energy, the action of a variety of mechanisms is built:

hydraulic brake;
hydraulic shock absorber;
hydraulic drive;
hydraulic pump.

The popularity of mechanisms of this kind in various fields of technology is due to the fact that huge energy can be transmitted with the help of quite simple device consisting of thin and flexible hoses. Industrial multi-ton presses, booms of cranes and excavators - all these irreplaceable machines in the modern world work efficiently thanks to hydraulics. Apart from industrial devices gigantic power, there are many manual mechanisms such as jacks, clamps and small presses.

How a hydraulic press works

To understand how this mechanism works, you need to remember what communicating vessels are. This term in physics refers to vessels interconnected and filled with a homogeneous liquid. The law of communicating vessels says that a homogeneous fluid at rest in communicating vessels is at the same level.

If we disturb the state of rest of the liquid in one of the vessels, for example, by adding liquid, or by applying pressure on its surface in order to bring the system to the equilibrium state that any system strives for, the liquid level will increase in the remaining vessels communicating with the given vessel. This happens on the basis of another physical law, named after the scientist who formulated it - Pascal's law. Pascal's law is as follows: the pressure in a liquid or gas is distributed equally to all points.

What is the principle of operation of any hydraulic mechanism? Why can a person easily lift a car weighing more than a ton to change a tire?

Mathematically, Pascal's law looks like this:

The pressure P is directly proportional to the applied force F. This is understandable - the harder you push, the greater the pressure. And inversely proportional to the area of the applied force.

Any hydraulic machine is a communicating vessel with pistons. circuit diagram and the hydraulic press device are shown in the photo.

Imagine that we have pressed a piston in a larger vessel. According to Pascal's law, pressure began to spread in the liquid of the vessel, and according to the law of communicating vessels, in order to compensate for this pressure, the piston rose in a small vessel. Moreover, if in a large vessel the piston has moved one distance, then in a small vessel this distance will be several times greater.

Conducting an experiment, or a mathematical calculation, it is easy to notice a pattern: the distance by which the pistons move in vessels of different diameters depends on the ratio of the smaller area of the piston to the large one. The same will happen if, on the contrary, force is applied to a smaller piston.

According to Pascal's law, if the pressure obtained by the action of the force applied to the unit area of the piston of the small cylinder is distributed equally in all directions, then the pressure will also be applied to the large piston, only increased by as much as the area of the second piston is larger than the area of the smaller one.

This is the physics and structure of the hydraulic press: the gain in strength depends on the ratio of the areas of the pistons. By the way, in a hydraulic shock absorber, the reverse ratio is used: a large force is damped by the shock absorber hydraulics.

The video shows the operation of a model of a hydraulic press, which clearly illustrates the operation of this mechanism.

The device and operation of the hydraulic press obeys the golden rule of mechanics: winning in strength, we lose in distance.

From theory to practice

Blaise Pascal, theoretically thinking through the principle of the hydraulic press, called it a "machine for increasing forces." But more than a hundred years have passed from the moment of theoretical research to practical implementation. The reason for this delay was not the uselessness of the invention - the benefits of the machine for increasing strength are obvious. Designers have made numerous attempts to build this mechanism. The problem was the difficulty of creating a sealing gasket that would allow the piston to fit snugly against the walls of the vessel and at the same time allow it to slide easily, minimizing friction costs - rubber did not exist then.

The problem was solved only in 1795, when the English inventor Joseph Bramah patented a mechanism called the Bramah press. This device was later called hydraulic press. The scheme of operation of the device, theoretically outlined by Pascal and embodied in Brahma's press, has not changed at all over the past centuries.

TO Category:

Pipelay Cranes

The principle of operation of the hydraulic system of attachments

General information. The hydraulic system of the attachment is designed to extend and retract the counterweight, as well as control the brakes and clutches. It consists of a hydraulic pump, hydraulic cylinders, hydraulic distributors, safety hydraulic valves, hydraulic throttles, hydraulic tanks, instrumentation (pressure gauges), hydraulic lines, and a filter.

In the considered pipelayers, the schemes of the hydraulic system of attachments, despite the use of unified assembly units and elements, have some differences due to the difference in the principle of switching on the winch drum control clutches and the presence of special load control devices.

Pipelayer T-3560M. From the tank (Fig. 85), the pump supplies the working fluid through line a to the distributor. In the neutral position of the spool handles, the working fluid through the holes in the distributor body enters the tank along the line. The distributor consists of three sections, two of which direct the flow of working fluid to the control cylinders for lifting and lowering the load clutch and boom control, and the third section serves the counterweight control cylinder. In the case of raising or lowering the handle (and with it the spool), the working fluid from the distributor through the throttles will flow into the right or left cavities of the cylinder, respectively pushing or pulling the counterweight.

Rice. 85. Hydraulic scheme of attachments of the T-3560L1 pipelayer:
1 - gear pump, 2 - safety valve, 3 - pressure gauge, 4 - three-spool distributor, 5 - counterweight control cylinder, b, 12, 13 - spool handles, 7 and 8 - cylinders for controlling the lifting and lowering clutches of the hook and boom, 9 - breaker, 10 - tank, 11 - chokes

When the handle is set to the neutral position (shown in the figure), the cylinder piston will be fixed in the position in which it was at the time the handle was moved.

When the handle is raised (shown in the figure), the working fluid from the distributor enters the left cylinder, which turns on the load lifting clutch and turns off the brake - the load begins to rise. When this handle is returned to the neutral position, the working fluid from the cylinder is directed back to the tank along the line and the load lifting clutch is turned off, and the brake brakes the drum. To lower the load, the handle is lowered, including the lowering clutch.

When the handle is raised, oil from the distributor enters the cylinder, which engages the boom lift clutch and releases the brake.

Rice. 86. Hydraulic scheme of attachments of the TT-20I pipelayer:
1 - block control panel, 2 - cylinder-sensor, 3 - cylinder automatic start» distributor, 4 7, 8, 10 - cylinders for controlling the lowering and raising clutches of the bunk and boom; 5, b, 12 - single-spool distributors, 9 - interrupter, 11 - counterweight control cylinder, 13 - gear pump, 14 - tank, 15, 19 - direct-acting safety valves, 16 - filter, P - differential-action safety valve, 18 - check valve, 20 - load device settings panel, 21 - throttle; 22 - load indicator

When the boom reaches the vertical position, the buffer device will press the breaker cam, the boom will stop lifting, since the oil through the breaker from the cylinder on the winch will go to the tank through the additional drain line e. In this case, the clutch will turn off and the brake will tighten. When lowering (shown in the figure) the arm, the boom) will lower.

The safety valve provides the pressure of the working fluid in the system necessary to control the winch and the counterweight - about 7800 kPa and bypasses the fluid from the pump to the tank along line r when this pressure is exceeded in the distributor.

Pipelayer TG-201. The working fluid pumped from the tank (Fig. 86) by the pump enters through line a to the spool valve. In the neutral position of the spool, the working fluid flows through the distributor simultaneously along lines b and c to single-spool distributors, and also reaches the differential action safety valve, which has remote unloading using line d. The liquid drains along this line, as well as line d, coming from the distributor into the tank with the distributors not switched on, passing through them in sequence.

When the distributor spool is moved to the right or to the left, the working fluid under pressure enters the rod or piston cavity of the hydraulic cylinder, providing for the advancing or tilting of the counterweight. As soon as the counterweight reaches the extreme position, the pressure in the hydraulic system will increase to the value to which the direct-acting safety valve is set, and the valve will work, starting to bypass liquid into the tank through line e. The supply of liquid and its discharge will stop after the distributor is turned off.

To turn on the cargo drum of the winch, it is necessary to move the distributor spool to the left or right. Line g of remote unloading will be blocked in the distributor and the working fluid will flow to the cylinders for switching on the couplings from line c. The pressure of the liquid when it is supplied to the cylinders will be limited by the setting value of the differential action safety valve, which, if the setting pressure is exceeded, will work and connect the line in with an additional drain line g, which has a filter.

The inclusion of the boom drum is carried out by moving the distributor spool. The working fluid will flow to the cylinders for switching on the boom drum clutches, and to the cylinder for switching on the boom lifting clutch - through the distributor-breaker. When the boom reaches the vertical position, it will press the breaker-distributor spool, the flow of working fluid to the cylinder will stop and the boom will automatically stop.

The pressure (4500 kPa) to which the differential action safety valve is set is less than the pressure (9500 kPa) of the direct action safety valve, since the cylinder and counterweight interacting with the valve and distributor require more pressure than the cylinders interacting with the valve and distributors.

All distributors and valves of the hydraulic system of the pipelayer are concentrated in the driver's cab in the form of a single control panel, which also includes a control panel for the load control device. This device includes a sensor cylinder that controls the load on the hook of the pipelayer, and a cylinder for automatic activation of the winch drum control distributor connected to the sensor cylinder.

Rice. 87. Hydraulic scheme of attachments of the TO-1224G pipelayer:
1 - filter, 2 - breaker, 3 and 4 - friction clutch control cylinders drive "winches and counterweight, 5 and 6 - two- and three-position distributors, 7 - pressure gauge, 8 - safety valve, 9 - gear pump, 10 - crane, 11 - tank

An increase in the load of the pipelayer leads to an increase in pressure in the rod end of the sensor cylinder, the line to and the piston end of the automatic actuation cylinder. Under the action of this pressure, the cylinder rod moves to the right. If, during its movement, the left of the two stops fixed on the rod reaches the distributor handle, the distributor will turn on and the supply of working fluid to the cylinder will begin, which will ensure the operation of the cargo drum to lower the pipeline. It uses characteristic the elastic state of the pipeline: with an increase in its upward deflection, the load from it increases, and with a decrease in the deflection, it decreases. As soon as the deflection of the pipeline as a result of the operation of the winch drum decreases, the pressure in the cylinders drops to normal, the contact between the left stop of the cylinder rod and the distributor handle under the action of the cylinder spring will stop and the distributor will turn off, and the winch drum will stop.

If the pressure in the sensor cylinder due to low external load falls below the norm, then the spring of the cylinder and the right stop fixed on its rod will turn on the distributor for the lifting rotation of the winch cargo drum.

The load monitor set-up panel includes a check valve, an adjustable direct acting relief valve, an adjustable throttle and a load indicator.

Pipelayer TO-1224G. The hydraulic system works as follows. With the pipelayer engine running and the power take-off turned on, the working fluid from the tank (Fig. 87) is pumped through line a to the three-position distributor. In the neutral position of the distributor spool, the working fluid flows out of it through the distributor and goes to the drain.

When the distributor spool is moved by the handle to one of the extreme positions, the working fluid begins to flow along lines d or e into one of the cylinder cavities, providing for the advancing or retracting of the counterweight. From the other cavity, the working fluid is displaced along opposite lines e or d, and then flows through the lines to the drain into the tank through the filter.

When the driver presses the handle of the two-position distributor, the non-pressure circulation of the working fluid through it stops and the fluid flows through the line w to the friction clutch control cylinder of the winch drive, ensuring the drive is turned on. With emphasis cargo boom into the buffer device of the upper frame and actuation of the distributor-breaker, the supply of working fluid to the cylinder is interrupted, since the working fluid begins to flow from line g to the drain line d and then to the tank.

In the event of an excessive increase in pressure in the hydraulic system, the safety valve and working fluid are activated along the line and enter the tank.