Pressure balancing system and pressure balancing method

Abstract

The invention discloses a pressure balancing system which is used for adjusting the pressure in a front cavity of a die plate of a granulator and comprises a hydraulic subsystem and a volume compensation mechanism, the hydraulic subsystem is connected with the volume compensation mechanism through a pipeline, and when the pressure in the front cavity of the die plate is smaller than the pressure of the hydraulic subsystem, the volume compensation mechanism extends into the front cavity of the die plate; and when the pressure in the front cavity of the template is greater than that of the hydraulic subsystem, the volume compensation mechanism moves towards the hydraulic subsystem. According to the pressure balance system, when the incoming material amount changes, the pressure in the front cavity of the template changes, so that the volume compensation mechanism compensates for the pressure change in the front cavity of the template through the pressure difference between the hydraulic subsystem and the front cavity of the template, and the problem that the pressure fluctuation of the front cavity of the template is large can be avoided; and the operation stability of the granulator is enhanced to a great extent. The invention further provides a pressure balancing method using the pressure balancing system.

Description

Technical Field

[0001] The invention relates to the technical field of pressure balance, and in particular to a pressure balance system and a pressure balance method for a pelletizer. Background Art

[0002] At present, during the use of the pelletizer, it is affected by the time it takes for the pressure transmitter in front of the template to receive the signal and feed it back to the frequency converter (such as DCS control, the pressure transmitter signal must be transmitted to the DCS, and the PID automatic control or manual control mode is used to send the instruction to the frequency converter), the frequency converter receives the signal and then instructs the motor to move, and the time it takes for the motor to start moving after receiving the frequency conversion instruction and complete the speed action. In the actual operation process, the pressure fluctuation in front of the pelletizer template caused by the change in the feed amount of the melt, pseudo-melt and other fluids is much faster than the reaction time of the melt pump (the compressibility of the melt, pseudo-melt and other fluids is small). In fact, large fluctuations in the pressure in front of the pelletizer template frequently occur in production operation. When the pressure fluctuation is large, it will cause a large change in the appearance of the material molding. When the pressure fluctuation is large enough, it will cause the pelletizer to malfunction and shut down.

[0003] Chinese patent document CN114393733A discloses a pelletizer section pressure compensation device, comprising an extruder head, a pelletizer mechanism and a fixed shell, wherein the fixed shell is cylindrical and mounted on the extruder head, and the pelletizer mechanism comprises a blade, which is rotatably arranged in the fixed shell near the die of the extruder head, and is characterized in that: it also includes an adjustment mechanism; the blade can move axially along the extruder head under the drive of the adjustment mechanism, and the pelletizer mechanism bears a constant thrust, so that the pressure between the blade and the die of the extruder head remains constant.

[0004] The prior art has the following deficiencies: the prior art uses a driving member to generate a constant thrust to improve the smoothness and reliability of the equipment, wherein the driving member uses a cylinder, so there is still a problem of the pelletizer malfunctioning and shutting down due to the untimely response of the driving member.

[0005] Another Chinese patent document CN204955354U discloses a three-channel feed die extrusion device, including a feed seat, a feed pipe, a connecting block and a die. The plastic melt enters the feed seat through a screw extruder, and the plastic melt is divided into three feed pipes on the left, middle and right sides through the three-forked flow channel inside the feed seat. The device can balance the melt pressure on both sides of the die, which can solve the problem of high shrinkage on both sides of the film.

[0006] The prior art has the following shortcomings: In the prior art, although the multi-channel method is used to divide the fluid pressure in front of the template and stabilize the pressure in front of the template holes at various positions of the template, the solution disclosed in the prior art is only applicable to the case where the incoming material volume is basically unchanged, and it is impossible to balance the overall pressure fluctuation in front of the template caused by changes in the incoming material volume. Summary of the invention

[0007] In order to solve the problem that the prior art cannot balance the overall pressure fluctuation in front of the template caused by changes in the incoming material amount, the present invention provides a pressure balancing system for adjusting the pressure in the front cavity of the pelletizer template, wherein: it includes a hydraulic subsystem and a volume compensation mechanism, the hydraulic subsystem and the volume compensation mechanism are connected by a pipeline, when the pressure in the front cavity of the template is less than the pressure of the hydraulic subsystem, the volume compensation mechanism extends into the front cavity of the template, and when the pressure in the front cavity of the template is greater than the hydraulic subsystem, the volume compensation mechanism moves toward the hydraulic subsystem.

[0008] In this solution, when the incoming material amount changes, the pressure in the front cavity of the template will change. Therefore, the volume compensation mechanism compensates for the pressure change in the front cavity of the template through the pressure difference between the hydraulic subsystem and the front cavity of the template, thereby avoiding the problem of large pressure fluctuations in the front cavity of the template and greatly enhancing the stability of the pelletizer operation.

[0009] Preferably, the volume compensation mechanism includes a volume compensation column, and the template front cavity is provided with a communication port, through which the volume compensation column extends into the template front cavity. In this solution, the pressure change in the template front cavity is compensated by extending the volume compensation column into or out of the template front cavity, and the structure is simple.

[0010] Preferably, the volume compensation mechanism also includes a connecting seat and a stopper, the volume compensation mechanism is connected to the front cavity of the template through the connecting seat, the stopper is connected to the connecting seat, and the volume compensation column passes through the stopper and the connecting seat in turn and then extends into the front cavity of the template through the connecting port. Considering that when the hydraulic subsystem suddenly loses pressure due to leakage or other reasons, the volume compensation column will move outward quickly, so in this solution, the connection seat and the stopper are used to limit the moving distance of the volume compensation column, so that the volume compensation column will no longer move outward after moving to the maximum limit distance on the stopper, which can avoid the problem of loss of pressure of the melt, pseudo-melt and other fluids in the front cavity of the template due to the excessive movement of the volume compensation column, resulting in interruption of pelletizing and continuous operation of the unit.

[0011] Preferably, the limiter is provided with a fixed limit flange for limiting the moving distance of the volume compensation column, and the outer surface of the volume compensation column is provided with a limit step matching the fixed limit flange. In this solution, the moving distance of the volume compensation column is limited by the cooperation of the fixed limit flange and the limit step, and the structure is simple.

[0012] Preferably, a sealing member is provided on the surface of the connection seat in contact with the stopper. In this solution, the provision of the sealing member can ensure the sealing in the hydraulic subsystem to ensure the normal use of the volume compensation mechanism, and the structure is simple.

[0013] Preferably, the hydraulic subsystem includes a booster pump connected to the volume compensation mechanism. In this solution, the booster pump is used to adjust the pressure of the hydraulic subsystem to adapt to the pressure in the front cavity of the template, and the structure is simple.

[0014] Preferably, the hydraulic subsystem further comprises an oil tank connected to the booster pump. In this solution, the pressure of the hydraulic subsystem can be adjusted by hydraulic oil by using the cooperation between the oil tank and the booster pump, and the structure is simple.

[0015] Preferably, the hydraulic subsystem further comprises an accumulator connected to the volume compensation mechanism. In this solution, the pressure of the hydraulic subsystem and pressure fluctuations can be stabilized or compensated by the accumulator, and the structure is simple.

[0016] Preferably, the hydraulic subsystem further comprises a safety valve for pressure relief protection in case of overpressure. In this solution, the setting of the safety valve can relieve pressure in case of overpressure to protect the pressure balance system.

[0017] In the second aspect, the present invention provides a pressure balancing method, which adopts any of the above-mentioned pressure balancing systems. When the pressure in the front cavity of the template is lower than the pressure of the hydraulic subsystem, the volume compensation mechanism extends into the front cavity of the template. When the pressure in the front cavity of the template is higher than the pressure of the hydraulic subsystem, the volume compensation mechanism moves toward the hydraulic subsystem.

[0018] The present invention has the following beneficial effects: 1. The present invention can automatically compensate for the pressure in the front cavity of the template through the cooperation of the volume compensation mechanism and the hydraulic subsystem, so that the pressure fluctuation in the front cavity of the template can be controlled within a certain range, which greatly improves the stability of the operation of the pelletizer. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of a pressure balancing system in an embodiment of a pressure balancing system and a pressure balancing method of the present invention; Figure 2 for Figure 1 Cross-sectional view of the mid-volume compensation mechanism. DETAILED DESCRIPTION

[0020] The following is further described in detail through specific implementation methods: 1. Definition Melt: molten material, a material in a molten state above the melting point. The melting point is the temperature at which a solid changes its physical state from solid to liquid (melts). It is affected by the magnitude of the pressure and the impurities in the substance. The melting point of a substance usually refers to a pure substance. Pseudo-melt: The material state is between the glass transition temperature and the melting point. Polymers will present three different physical states at different temperatures: glassy state, highly elastic state, and viscous flow state; Compressibility: The property that the volume or density of a fluid particle can change under certain pressure or temperature differences. Its physical meaning is the rate of change of the volume of a unit volume of fluid to the pressure, which means that the volume decreases when the pressure increases.

[0021] 2. Publicly known technology and its source Liquids are very compressible at normal pressure or temperature. The compressibility of a fluid is expressed by the compression coefficient K. For example, water shrinks by 0.5% at 100 atmospheres (1 atmosphere = 101 325 Pa); when the temperature changes from 20°C to 100°C, the volume decreases by 4%. "Fluid Dynamics (2nd Edition)" is a book published in 2013, written by Chen Yupu and Wang Huimin.

[0022] 3. The figure marks in the drawings of the specification include: oil tank 11, booster pump 12, safety valve 13, accumulator 14, piston cylinder 2, volume compensation mechanism 3, connecting seat 31, volume compensation column 32, limit step 320, fixed limit flange 33, template front cavity 4.

[0023] The embodiment is basically as shown in the attached Figure 1 As shown: a pressure balancing system for adjusting the pressure in the front cavity 4 of the pelletizer template, including a hydraulic subsystem and a volume compensation mechanism 3. The hydraulic subsystem is connected to the volume compensation mechanism 3 through a pipeline. When the pressure in the front cavity 4 of the template is less than the pressure of the hydraulic subsystem, the volume compensation mechanism 3 extends into the front cavity 4 of the template. When the pressure in the front cavity 4 of the template is greater than the pressure of the hydraulic subsystem, the volume compensation mechanism 3 moves toward the hydraulic subsystem.

[0024] Specifically, Figure 2 As shown, the volume compensation mechanism 3 includes a piston cylinder 2, a volume compensation column 32, a connecting seat 31 and a stopper. The piston cylinder 2 drives the volume compensation column 32 to move. The connecting seat 31 is arranged on the front cavity 4 of the template. The front cavity 4 of the template is provided with a connecting port. The volume compensation column 32 passes through the stopper and the connecting seat 31 in sequence and then extends into the front cavity 4 of the template through the connecting port. The stopper is provided with a fixed limiting flange 33 for limiting the moving distance of the volume compensation column 32. The outer surface of the volume compensation column 32 is provided with a limiting step 320 matching the fixed limiting flange 33. The surface of the connecting seat 31 in contact with the stopper is provided with a sealing member.

[0025] The hydraulic subsystem includes a booster pump 12, an oil tank 11, an accumulator 14 and a safety valve 13 connected by pipelines. The booster pump 12, the oil tank 11, the accumulator 14 and the safety valve 13 are connected by pipelines.

[0026] The specific implementation process is as follows: before use, the hydraulic oil in the oil tank 11 is pressurized by the booster pump 12 and then added to the hydraulic subsystem to reach the required pressure of the fixed volume cavity in front of the template. Nitrogen gas with a pressure higher than the set pressure is filled in the accumulator 14. When the pressure of the melt, pseudo-melt and other fluids in front of the template fluctuates greatly due to the fluctuation of the feeding amount, the pressure of the melt, pseudo-melt and other fluids in the cavity rises when the feeding amount is large. Since the pressure of the hydraulic subsystem will be less than the pressure of the cavity 4 in front of the template, the volume compensation column 32 is pushed to move out of the cavity; when the feeding amount decreases, since the pressure of the hydraulic subsystem will be greater than the pressure of the cavity 4 in front of the template, the hydraulic subsystem pushes the volume compensation column 32 to move into the cavity.

[0027] In the above process, the large fluctuation of pressure in the front cavity 4 of the template caused by the fluctuation of the feeding amount is self-regulated by the volume compensation column 32, dynamically ensuring that the pressure in the front cavity 4 of the template is reduced by the fluctuation of the feeding amount, achieving a relatively stable effect, ensuring the continuous and stable operation of the pelletizer, and ensuring the continuous operation of the unit and the device.

[0028] When the hydraulic subsystem suddenly loses pressure due to leakage or other reasons, the volume compensation column 32 moves outward quickly. When the end reaches the inner wall of the template front cavity 4, the volume compensation column 32 presses on the limiter and no longer moves outward, which will not cause the melt, pseudo-melt and other fluids in the template front cavity 4 to lose pressure, thereby interrupting the continuous operation of the pelletizing unit.

[0029] The above is only an embodiment of the present invention. The common sense such as the known specific structure and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field know all the common technical knowledge in the technical field of the invention before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A pressure balance system for adjusting the pressure in the front cavity of a pelletizer template, characterized in that: It includes a hydraulic subsystem and a volume compensation mechanism, wherein the hydraulic subsystem is connected to the volume compensation mechanism through a pipeline, and when the pressure in the front cavity of the template is less than the pressure of the hydraulic subsystem, the volume compensation mechanism extends into the front cavity of the template, and when the pressure in the front cavity of the template is greater than the pressure of the hydraulic subsystem, the volume compensation mechanism moves toward the hydraulic subsystem.

2. The pressure balancing system according to claim 1, characterized in that: The volume compensation mechanism includes a volume compensation column. The template front cavity is provided with a communication port, and the volume compensation column extends into the template front cavity through the communication port.

3. The pressure balancing system according to claim 2, characterized in that: The volume compensation mechanism also includes a connecting seat and a limiter. The volume compensation mechanism is connected to the front cavity of the template through the connecting seat. The limiter is connected to the connecting seat. The volume compensation column passes through the limiter and the connecting seat in sequence and then extends into the front cavity of the template through the connecting port.

4. The pressure balancing system according to claim 3, characterized in that: The limiter is provided with a fixed limit flange for limiting the moving distance of the volume compensation column, and the outer surface of the volume compensation column is provided with a limit step matching the fixed limit flange.

5. The pressure balancing system according to claim 4, characterized in that: A sealing member is provided on the surface of the connection seat in contact with the stopper.

6. The pressure balancing system according to any one of claims 1 to 5, characterized in that: The hydraulic subsystem includes a boost pump connected to the volume compensation mechanism.

7. The pressure balancing system according to claim 6, characterized in that: The hydraulic subsystem further includes an oil tank connected to the boost pump.

8. The pressure balancing system according to claim 7, characterized in that: The hydraulic subsystem also includes an accumulator connected to the volume compensation mechanism.

9. The pressure balancing system according to claim 8, characterized in that: The hydraulic subsystem also includes a safety valve for pressure relief protection in case of overpressure.

10. A pressure balancing method, characterized in that: Using the pressure balancing system as described in any one of claims 1 to 9, when the pressure in the front cavity of the template is lower than the pressure of the hydraulic subsystem, the volume compensation mechanism extends into the front cavity of the template, and when the pressure in the front cavity of the template is higher than the pressure of the hydraulic subsystem, the volume compensation mechanism moves toward the hydraulic subsystem.

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