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    hydraulic piston pump

    hydraulic piston pump

    Hydraulic piston pumps are the most expensive and, at the same time, the most durable hydraulic pumps. These types of pumps are used in both open circuit and close circuits in the industrial and mobile hydraulic field. The hydraulic piston pump is the best and most suitable choice for use in circuits with a high working pressure of up to 700 bar. In this type of pumps, the tolerance between the pistons and the cylinder is very low, and the low tolerance between the piston and the cylinder makes this type of pump less tolerable than other hydraulic pumps. In order to increase the life of the pump, the two components of the purification of the pump oil and Non-contamination of the pump's work environment is very important.



     axial piston pump

    These types of pumps are designed in such a way that the pistons return when they pass through the inlet opening, in other words, moving the piston back into the cylinder, creating more space and, consequently, lowering the atmospheric pressure and creating a vacuum, and in Ultimately, oil can be introduced into pump compartments. Then, in the outlet, perform the "go" and direct the oil by pushing the system.

    Hydraulic piston pumps are divided into two types based on the type of piston mechanism and arrangement:
    ⦁ Axial Piston Pump
    ⦁ Radial Piston Pump

    Hydraulic Axial piston pump

    In this type of pump, the rotary axis and cylinder block are located on a central line. That is, the pistons are parallel to the pump axis and the pistons are arranged around the pump axis. The rotation of the pump axis causes the pistons to rotate and the cylinder block.
    The sweep of the pistons is done by the angled plate and when the cylinder block is rotated, the pistons that are in contact with the swash plate, which causes the pump to rotate when the pump axis is rotated, The pistons also operate inside the cylinder block. At the first 180 degrees of the pump's axis of rotation, at the point where the pistons start to return (pull back), the open end of the cylinder, slipping against the input groove located on the valve plate.
    Therefore, oil is drained less than halfway through the cylinder and the oil suction process takes place. When the piston is fully reversed, the open end of the cylinder ends in front of the closed part and without the valve plate groove. During 180 degrees, the piston rotation of the pump axis means that as soon as the pistons start "going", the open end of the cylinder is guided to the side of the groove (in the form of a semicircle) of the outlet and releases the oil by pressure from the outlet. Rand In the following figure, a schematic illustration of the hydraulic piston pump operation process is presented.


    piston pump

    Hydraulic axial piston pumps are designed in two ways:
    ⦁ Swash Plate
    ⦁ Bent Axis


    Swash Plate piston pump

    Step 1:

    Axial piston pumps converge the rotation of the inlet axis to the reciprocating motion of the pistons inside the cylinder. This function is supplied by a swash plate that can be fixed or variable angles. Due to the time of the piston-bearing enclosure, the pistons also rotate around the axis and, because of being in contact with the angle plate, they are guided to the front and rear.

    Step 2:

    When the swash plate is in a vertical position, there will be no movement and return movement. By increasing the angle of the swash plate, the pistons are guided to the outside of the cylinder.

    Step 3:

    Actually, the cylinder block has a number of pistons. During one half of the movement around the pump axis, the pistons move to the outside of the cylinder compartment and the volume of the cylinder inside the cylinder decreases. During this reciprocating action, the oil is drained inside the cylinder and then poured out of the cylinder.
    In this type of pumps, the axis of the cylinder block and drive axis are located along the center line. When the cylinder block is rotated, the pistons move back and forth due to the position of the angular position plate. The oil inlet and outlet ports are connected via a separator plate to the cylinder block. The pistons pass through the inlet and outlet ports, respectively, when moving to and out of the respective cylinders, respectively.

    The following illustrates the components of the axial piston pump:


    piston pump

    Fundamentals of Hydraulic

    Variable displacement axial

    Tip 1:

    The displacement volume of a piston pump can be determined by knowing the displacement course length of each piston, the diameter of each piston and the number of pistons. By inserting a mechanism for changing the angle of the back plate of the pistons, the displacement volume of a pump can be changed. As in the figure below, this mechanism actually changes the piston movement course.


    Tip 2:

    Axial piston pumps can also be designed with variable displacement properties. In the type of displacement, the position of the angular position plate is adjusted by manual mechanisms, automatic control, or through the compensation system. The maximum angle to the angle plate is 17.5 degrees.
    Among the major manufacturers of these types of pumps are the three Rexorth Companies in Germany, Parker (Denison-Parker) and American Eaton Vickers.

    Bent axis hydraulic piston pump

    In this type of piston pump, the piston shafts are connected to spherical balls that are located in the actuator axis. A universal coupling connects the cylinder block to the axis so that they rotate, but they are angular. The cylindrical block is in contact with the slotted valve plate where the ducts are connected.
    These types of pumps are suitable when there is a limitation of the installation space for the pump.
    In the figure below, the hydraulic piston pump of the bent axis is shown.


    bent axis pump


    Radial Piston Pump

    The radial piston pump building includes a cylinder block with associated pistons, a reaction rim and a tap on the central part of the rotor. The pistons are mounted radially in the main shell and placed under the spring loading on an outboard center bearing. The pistons are always in contact with the surface of the rim by centrifugal force and the pressure of the fluid behind them.




    The pistons are placed on a cylindrical, short, radially, like a blade of a wheel in the crust. This cylindrical part (including pistons and piston block) is driven by rotary axes that are circular in a circular compartment. If the shell and the level of the cam are fixed. Due to the fact that the outside of the center between the piston block and the level of the cams creates a motorcycle for the pistons. Turning this cylinder block itself onto a fixed rod that includes inlet and outlet ports, and these inlet and outlet openings are also separated by a non-rotating separator blade. Thus, when the cylindrical part is circulating, the centrifugal force causes the pistons to be thrown outwards and are always shaped by continuous contact with a circular compartment. In order to pump the oil, it must be located in a non-center position relative to the rotor axis. As a result of the rotation of the cylinder block and out of the center, the pistons move one side to the outside and the pistons on the other side move towards the center of the rotor.


    radial piston pump 2


    In the area where the pistons move away from the center of the rotor, a suction is required. The fluid can be guided through the central duct into the relevant cylinders. When the piston passes from the maximum position outside of the center and moves into the cylinder, due to the function of the reaction rim, and reduces the volume. Eventually, this piston displacement drives the fluid towards the central valve outlet. As a result of centrifugal force and fluid pressure, they are always in contact with the surface of the rim.
    In a variety of variable displacements, the displacement of the piston changes as the volume displacement of the pump changes. Therefore, the central axis of this chamber is located at a certain distance from the central axis of the cylindrical parts. This distance is the distance the piston can change and necessarily determines the displacement of the pump. When the piston returns due to the connection and connection of the one tap to the reservoir, fluid suction is performed and the piston is pumped when the piston is pushed due to the connection of the unbalanced tap to the outlet.
    In the following figure, a radial hydraulic piston pump of varying type is shown.


    radial piston pump

    Maintaining and preventing possible defects in the hydraulic piston pump


    Each manufacturer provides instructions that the regular implementation of these rules will increase the lifetime of the pump as well as the high pump efficiency during its operating cycle. In the following, some of these instructions are for maintenance and proper operation of axial piston pump and radial piston pump.


    Maintenance and prevention of possible defects in an axial piston and radial piston pumps

    1. Check the oil level in the tank daily.
    2. Check the temperature of the work when the system is under load at the input of the tank and inside the tank on a weekly basis.
    3. The oil system analysis is based on the viscosity index, the amount of oil working hours and the amount of contamination annually or every 2,000 hours of work.
    4. Keep the pump in clean condition and check for leakage without any leakage.
    5. Pay attention to the pump's sound during the work on a daily basis. Check for possible abnormalities when creating an abnormal sound.
    6. When the system is off and cool, all connections are checked monthly for tightness and non-leakage.

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