Roll die gap self-adaptive force control hydraulic system of ring die granulator

Abstract

The invention provides a self-adaptive force control hydraulic system for a roller die gap of a ring die granulator, and relates to a hydraulic control system of the ring die granulator, the self-adaptive force control hydraulic system has two working modes of a position control mode and a force control mode, and the gap between a compression roller and a ring die can be automatically adjusted through a hydraulic cylinder so as to improve the working efficiency and the stability of the granulator. In the position control mode, the gap can be locked after gap debugging is completed, the size of the gap is not changed in the working process, and in the force control mode, the displacement of the piston of the hydraulic cylinder directly reflects the amount of accumulated materials between the compression roller and the ring die, so that the feeding speed can be controlled according to the displacement of the piston of the hydraulic cylinder, and the pressure of a hydraulic system does not change remarkably.

Description

Technical Field

[0001] The invention relates to a hydraulic control system for a ring die pelletizer, in particular to a ring die pelletizer roller die gap adaptive force control hydraulic system which can provide two working modes, position control and force control, and is used for optimizing the gap adjustment between a pressure roller and a ring die. Background Art

[0002] A pellet mill is a mechanical device used to process raw materials into granules. It is widely used in feed, fertilizer, fuel and other industries. In the operation of a pellet mill, the gap between the roller and the ring die is quite critical. This gap not only affects the efficiency of pelleting and the quality of the product, but also involves the maintenance and service life of the equipment, which is specifically reflected in:

[0003] 1) Appropriate gap can effectively ensure that the raw materials are extruded smoothly in the ring die hole, thereby improving production efficiency. If the gap is too large, the pressure exerted by the roller on the raw materials is insufficient, the granulation effect is poor, and the efficiency is reduced; if the gap is too small, the raw materials are too compacted between the roller and the ring die, which increases energy consumption and may cause the ring die hole to be blocked, and even shut down in serious cases;

[0004] 2) The appropriate roller-die gap can produce particles with uniform shape and density to meet different application requirements. If the gap is not properly controlled, the particles may break and pulverize, affecting the quality of the finished product.

[0005] 3) Appropriate gap can ensure efficient use of energy during pelletizing and reduce unnecessary energy waste. Too small a gap will increase the friction between the roller and the die, leading to increased wear of the equipment, increased maintenance costs and equipment downtime;

[0006] 4) Appropriate gap setting can reduce excessive wear of the pressure roller and ring die, thereby extending their service life and reducing the frequency of replacement of accessories.

[0007] Based on this, it can be seen that the control of the roller-die gap plays an important role in granulation production. Generally speaking, the setting of the roller-die gap needs to be considered based on the following factors:

[0008] a. Material properties: The hardness, water content, particle size, etc. of different materials will affect the setting of the roller die gap;

[0009] b. Equipment model: Different models of pelletizers have different designs, and the recommended settings for the roller-die gap will also be different;

[0010] c. Production requirements: According to specific production requirements, such as particle size and yield rate, the roller-die gap should be adjusted appropriately;

[0011] In the gap adjustment structure of the pelletizer: the roller consists of a roller shaft and a roller wheel. The roller wheel can rotate freely relative to the roller shaft. The roller shaft is an eccentric shaft. The hydraulic cylinder (or other driving mechanism) pushes the roller shaft to rotate, which will change the gap between the roller and the ring die. After adjusting to the target gap, the hydraulic cylinder is locked (through a hydraulic valve) to keep the gap between the roller and the ring die unchanged. Under normal circumstances, the common roller-die gap range is as follows (the specific setting needs to be adjusted and tested according to the actual situation):

[0012] Ordinary materials: The gap between the roller and the die is generally between 0.1-0.3 mm.

[0013] High hardness materials: The gap between the roller and the die should be increased appropriately, and can be between 0.3-0.5 mm.

[0014] Soft materials: The gap between the roller and the die can be adjusted to a smaller value within the range of 0.05-0.1 mm;

[0015] The common granulator roller die gap adjustment mechanisms include:

[0016] 1) Screw adjustment mechanism - adjust the working length of the screw by rotating the hand wheel or handle to change the distance between the roller and the die. After adjustment, the screw is locked and the gap remains unchanged;

[0017] 2) Gasket adjustment mechanism - use gaskets of different thicknesses to adjust the gap between the roller dies by adding or reducing gaskets. After adjustment, the screw is locked and the gap remains unchanged;

[0018] 3) Servo motor adjustment mechanism - use the servo motor to drive the worm gear mechanism to adjust the gap. After adjustment, the worm gear mechanism will self-lock and the gap will remain unchanged.

[0019] 4) Pneumatic adjustment mechanism: the worm gear mechanism is driven by the cylinder and valve system to adjust the gap. After adjustment, the worm gear mechanism is self-locking and the gap remains unchanged;

[0020] 5) Hydraulic adjustment mechanism - the hydraulic cylinder adjusts the hydraulic pressure and stroke through the control system to change the roller die gap. After adjustment, the hydraulic cylinder is locked and the gap remains unchanged (but if the system pressure exceeds the safety pressure, it can be unloaded through the overflow valve);

[0021] The above five types of roller-die gap adjustment mechanisms of pellet mills are all position controlled. After adjustment, the gap remains unchanged. The first four types lock the gap through a mechanical system. As long as the drive system does not move, the gap will not change with the change of load. If foreign matter enters between the roller and the ring die, there is a risk of damage to the roller or the ring die. The fifth type of hydraulic drive, due to the presence of the overflow valve (safety valve), when foreign matter enters between the roller and the ring die, causing the hydraulic system to rise, the overflow valve is unloaded, the piston rod of the hydraulic cylinder is retracted, and the roller-die gap is increased, which can significantly reduce the risk of damage to the roller or the ring die.

[0022] Based on this, we found that the above-mentioned defects and shortcomings still exist:

[0023] The characteristics of feed processing are that there are many types of raw materials, many formulas, and the content of raw materials fluctuates greatly. Therefore, the moisture content, viscosity and fluidity of the feed mixture fluctuate greatly. The common gap between the roller and the die of the pelletizer remains unchanged after being adjusted in place, and cannot be adjusted adaptively according to the material characteristics. For example, if the moisture content of the material is higher than the upper limit, the adhesion between the ring die and the pressure roller will deteriorate, resulting in slippage between the pressure roller and the ring die (the speed of the pressure roller decreases), and the material cannot be extruded from the ring die hole or the extrusion speed decreases. Continuous feeding increases the accumulation of material between the pressure roller and the ring die, and eventually the ring die is stuck (this fault occurs very frequently, once every 6-8 hours on average, and the fault handling causes about 1 hour of work delay). Therefore, a ring die pelletizer roller gap adaptive force control hydraulic system that can provide two working modes, position control and force control, is used to optimize the adjustment of the gap between the pressure roller and the ring die;

[0024] We also conducted further searches based on this and found related patents: a hydraulic roller die of a ring die pelletizer with adjustable roller die gap (Announcement No. CN112619556A), a granulator adjustment mechanism (Announcement No. NL9302236A), and an automatic adjustment device for the gap between the rollers of a ring die pelletizer (Announcement No. CN115106016A). In the comparison, we found that:

[0025] In contrast, the hydraulic system of the patent CN112619556A A Hydraulic Roller Die for Ring Die Granulator with Adjustable Roller Die Gap is relatively simple, and its characteristics are that "the rod chamber of the hydraulic cylinder 8 is connected to the relief valve 36, and the rodless chamber of the hydraulic cylinder 8 is connected to the accumulator 34. When the granulator is in operation, if a foreign object enters between the roller and the ring die, the pressure in the rod chamber of the hydraulic cylinder 8 increases, and after exceeding the set pressure of the relief valve 36, the pressure is unloaded, the oil in the rod chamber returns to the oil tank, and the accumulator replenishes oil to the rodless chamber of the hydraulic cylinder 8". Because the rod chamber of the hydraulic cylinder 8 is the working pressure, the accumulator 34 is connected to the rodless chamber of the hydraulic cylinder 8, which cannot play a role in stabilizing the pressure. The core of this patent is the force control mode, and it also has the protection function of foreign object entry.

[0026] The comparative patent "NL9302236A Pellet mill adjustment mechanism" is the earliest pneumatically driven roller die gap adjustment mechanism patent found so far. Another comparative patent "CN115106016A Ring die pellet mill die roller gap automatic adjustment device" is a simplified design of the patent mechanism. These two patents use different drive and transmission methods from this patent and do not have a force control mode, so there is no conflict. Summary of the invention

[0027] The present invention provides the following technical solutions:

[0028] The invention discloses a roller-die gap self-adaptive force control hydraulic system for a ring die pelletizing machine, which has two working modes, namely, a position control mode and a force control mode, and can automatically adjust the gap between the pressure roller and the ring die through a hydraulic cylinder.

[0029] Preferably, the system also has a switching mode between high pressure and low pressure, and the switching between the high pressure mode and the low pressure mode is performed through solenoid valve 1. When solenoid valve 1 is switched to its first working position, overflow valve 1 is turned on, and overflow valve 1 is used to prevent system overload in the high pressure mode. When solenoid valve 1 is switched to its second working position, overflow valve 2 is turned on, and overflow valve 2 is used to prevent system overload in the low pressure mode.

[0030] Preferably, the position control mode and the force control mode are switched between two positions through solenoid valve 2. When solenoid valve 2 is switched to its first working position, the system is in the position control mode, and when solenoid valve 2 is switched to its second working position, the system is in the force control mode.

[0031] Preferably, in the position control mode, the system adjusts the working state of the hydraulic cylinder through solenoid valve three to adjust the gap between the pressure roller and the ring die. When solenoid valve three is switched to its second working position, oil enters the rodless chamber of the hydraulic cylinder and the piston rod extends. When solenoid valve three is switched to its third working position, oil enters the rod chamber of the hydraulic cylinder and the piston rod retracts. The throttle valve in the system oil circuit is used to limit the oil return speed of the rodless chamber of the hydraulic cylinder to make the extension and retraction speeds of the piston rod consistent. When solenoid valve three is switched to its first working position, the rodless chamber and the rod chamber of the hydraulic cylinder are locked.

[0032] Preferably, to ensure the safety of the hydraulic system, an overflow valve three is also installed on the oil return line of the rodless chamber of the hydraulic cylinder. During the operation of the system, if a hard object enters between the pressure roller and the ring die, causing the pressure of the hydraulic system to exceed the set pressure of the overflow valve three, the overflow valve three will unload and the hydraulic cylinder piston rod will retract, thereby avoiding damage to the pressure roller or the ring die.

[0033] Preferably, in the force control mode, the rodless chamber and the rod chamber oil circuits of the hydraulic cylinder are connected, the thrust of the hydraulic cylinder is determined by the hydraulic system pressure and the working area of ​​the hydraulic cylinder, the accumulator is used to stabilize the hydraulic system pressure, and the displacement of the hydraulic cylinder piston rod is used to reflect the material accumulation condition between the pressure roller and the ring die and control the feeding speed.

[0034] Preferably, in the force control mode, the solenoid valve three is only in its second working position or the third working position.

[0035] Preferably, the system also has an unloading mode. In both the position control mode and the force control mode, the manual valve is in its first working position, and in the unloading mode, the manual valve is in its second working position. At the same time, when the solenoid valve three is in its first working position, only the hydraulic cylinder is unloaded, and when the solenoid valve three is in its second working position or its third working position, the accumulator and the hydraulic cylinder are unloaded at the same time.

[0036] Preferably, when the hydraulic system is switched from the high-pressure mode to the low-pressure mode, the accumulator needs to be unloaded first.

[0037] Preferably, it also includes an oil tank, a hydraulic pump, a one-way valve 1, a one-way valve 2, a one-way valve 3, and a filter. The solenoid valve 1, the solenoid valve 2, and the solenoid valve 3 are connected in parallel between the hydraulic pump and the hydraulic cylinder, and the one-way valve 1 is used for unidirectional conduction of the oil circuit that synchronously enters the solenoid valve 2 and the solenoid valve 3, and the one-way valve 1 is also arranged in parallel with the solenoid valve 1. An accumulator and a pressure gauge are arranged on the one-way valve 1 unidirectional conduction of the oil circuit that synchronously enters the solenoid valve 2 and the solenoid valve 3. The one-way valve 2 is used for unidirectional conduction of the oil circuit that enters the oil tank, and the oil at the oil circuit receiving end of the one-way valve 2 comes from the manual valve when it is in its second working position or from the manual valve when the solenoid valve 3 is in its first working position. The solenoid valve 2 is in its first working position, the oil circuit where the solenoid valve is located is connected in parallel with the one-way valve, which is connected in parallel with the overflow valve 1 and the overflow valve 2 to perform parallel unloading with the one-way valve 2, and the one-way valve 3 is provided with three groups, the first group of one-way valves 3 is used for one-way conduction of the oil circuit from the rod chamber of the hydraulic cylinder into the manual valve, the second group of one-way valves 3 is used for one-way conduction of the oil circuit from the rodless chamber of the hydraulic cylinder into the manual valve, and the conducting paths of the first group of one-way valves 3 and the second group of one-way valves 3 are opposite, the throttle valve is connected in the oil circuit flowing from the rodless chamber of the hydraulic cylinder to the overflow valve 3 and the solenoid valve 3, and the third group of one-way valves 3 are connected in parallel at both ends of the throttle valve, and its conducting path is the same as that of the second group of one-way valves 3.

[0038] The beneficial effects of the present invention are:

[0039] The present invention relates to a hydraulic control system for the gap between a pressure roller and a ring die of a ring die pelletizer, the system provides two working modes, namely position control and force control, to improve the working efficiency and stability of the pelletizer;

[0040] In the position control mode, the system can adjust the gap between the pressure roller and the ring die by adjusting the working state of the hydraulic cylinder. When the gap is debugged, the gap can be locked to ensure that the gap size between the pressure roller and the ring die remains unchanged during the working process. To ensure the safety of the hydraulic system, a relief valve 3 is also installed on the oil return line of the rodless chamber of the hydraulic cylinder. During the operation of the system, if a hard object enters between the pressure roller and the ring die, causing the pressure of the hydraulic system to exceed the set pressure of the relief valve 3, the relief valve 3 will unload and the piston rod of the hydraulic cylinder will retract, thereby avoiding damage to the pressure roller or the ring die.

[0041] In the force control mode, the oil circuits of the rodless chamber and the rod chamber of the hydraulic cylinder are connected, and the thrust of the hydraulic cylinder is proportional to the pressure of the hydraulic system. The pressure of the hydraulic system and the effective working area of ​​the rodless chamber and the rod chamber of the hydraulic cylinder work together to enable the hydraulic cylinder to achieve precise force control. The hydraulic system is also equipped with an accumulator to stabilize the pressure of the hydraulic system. In this mode, the displacement of the hydraulic cylinder piston rod directly reflects the amount of material accumulation between the pressure roller and the ring die, so that the feeding speed can be controlled according to the displacement of the hydraulic cylinder piston rod, and the pressure change of the hydraulic system is not significant;

[0042] 1) If the material accumulation between the pressure roller and the ring die increases, the piston rod of the hydraulic cylinder will retract, and the gap between the pressure roller and the ring die will increase, which can avoid the ring die from getting stuck and provide time to reduce the feeding speed and reduce the material accumulation;

[0043] 2) If the material accumulation between the pressure roller and the ring die is reduced, the piston rod of the hydraulic cylinder will extend, and the gap between the pressure roller and the ring die will be reduced (until the pressure roller and the ring die are in direct contact), and the pressure roller can be prevented from slipping;

[0044] If there is foreign matter between the pressure roller and the ring die, the piston rod of the hydraulic cylinder will retract quickly, and the control system can determine whether there is foreign matter entering the pressure roller according to the displacement change of the hydraulic cylinder piston. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0046] Figure 1 It is a schematic diagram of the hydraulic system oil circuit in which a hydraulic cylinder drives two pressure rollers at the same time;

[0047] Figure 2 It is a schematic diagram of the oil circuit in a hydraulic system in which two hydraulic cylinders drive two pressure rollers when the solenoid valve is turned on in high pressure mode;

[0048] Figure 3 This is the oil circuit diagram when the solenoid valve is in low-pressure mode;

[0049] Figure 4It is a schematic diagram of the oil circuit of the hydraulic system marking prominent position control mode;

[0050] Figure 5 It is a schematic diagram of the oil circuit of the hydraulic system marking the protruding force control mode;

[0051] Figure 6 It is a schematic diagram of the oil circuit that indicates that only the hydraulic cylinder is unloaded in the position control mode;

[0052] Figure 7 It is a schematic diagram of the oil circuit showing that both the hydraulic cylinder and the accumulator are unloaded in the position control mode;

[0053] Figure 8 This is a schematic diagram showing the gap adjustment between the pelletizer roller and the ring die;

[0054] Markings in the figure:

[0055] 1. Oil tank; 2. Hydraulic pump; 3. One-way valve 1; 4. Accumulator; 5. Pressure gauge; 6. Solenoid valve 1; 7. Solenoid valve 2; 8. Solenoid valve 3; 9. Overflow valve 1; 10. Overflow valve 2; 11. Overflow valve 3; 12. Filter; 13. One-way valve 2; 14. One-way valve 3; 15. Throttle valve; 16. Manual valve; 17. Hydraulic cylinder; 18. Piston rod; 19. Press roller; 20. Ring die. DETAILED DESCRIPTION

[0056] like Figure 1-8 As shown, a ring die pelletizer roller die gap adaptive force control hydraulic system, in this embodiment, has two working modes: position control mode and force control mode, and can automatically adjust the gap d between the pressure roller 19 and the ring die through the hydraulic cylinder 17.

[0057] The system also has a switching mode between high pressure and low pressure, and the switching between the high pressure mode and the low pressure mode is performed through the solenoid valve 6. When the solenoid valve 6 is switched to its first working position, the overflow valve 9 is turned on, and the overflow valve 9 is used to prevent the system from overloading in the high pressure mode. When the solenoid valve 6 is switched to its second working position, the overflow valve 2 10 is turned on, and the overflow valve 2 10 is used to prevent the system from overloading in the low pressure mode.

[0058] The position control mode and the force control mode are switched between two positions by the solenoid valve 27. When the solenoid valve 27 is switched to its first working position, the system is in the position control mode, and when the solenoid valve 27 is switched to its second working position, the system is in the force control mode.

[0059] In the position control mode, the system adjusts the working state of the hydraulic cylinder 17 through the solenoid valve 38 to adjust the gap between the pressure roller 19 and the ring die 20. When the solenoid valve 38 is switched to its second working position, oil enters the rodless chamber of the hydraulic cylinder 17 and the piston rod 18 extends. When the solenoid valve 38 is switched to its third working position, oil enters the rod chamber of the hydraulic cylinder 17 and the piston rod 18 retracts. The throttle valve 15 in the system oil circuit is used to limit the oil return speed of the rodless chamber of the hydraulic cylinder 17, so that the extension and retraction speeds of the piston rod 18 are consistent. When the solenoid valve 38 is switched to its first working position, the rodless chamber and the rod chamber of the hydraulic cylinder 17 are locked.

[0060] To ensure the safety of the hydraulic system, an overflow valve 3 11 is installed on the oil return line of the rodless chamber of the hydraulic cylinder 17. During the operation of the system, if a hard object enters between the pressure roller 19 and the ring die 20, causing the pressure of the hydraulic system to exceed the set pressure of 300 bar of the overflow valve 3 11, the overflow valve 3 11 will unload and the piston rod 18 of the hydraulic cylinder 17 will retract, thereby avoiding damage to the pressure roller 19 or the ring die 20.

[0061] In the force control mode, the oil circuits of the rodless chamber and the rod chamber of the hydraulic cylinder 17 are connected, the thrust of the hydraulic cylinder 17 is determined by the hydraulic system pressure and the working area of ​​the hydraulic cylinder 17, the accumulator 4 is used to stabilize the hydraulic system pressure, and the displacement of the piston rod 18 of the hydraulic cylinder 17 is used to reflect the material accumulation condition between the pressure roller 19 and the ring die 20, and to control the feeding speed.

[0062] In the force control mode, the solenoid valve 3 8 is only in its second working position or the third working position.

[0063] The system also has an unloading mode. In both the position control mode and the force control mode, the manual valve 16 is in its first working position, and in the unloading mode, the manual valve 16 is in its second working position. At the same time, when the solenoid valve three 8 is in its first working position, only the hydraulic cylinder 17 is unloaded, and when the solenoid valve three 8 is in its second working position or its third working position, the accumulator 4 and the hydraulic cylinder 17 are unloaded at the same time. At this time, it is necessary to ensure that the hydraulic pump 2 is in the closed state and the hydraulic oil in the accumulator 4 will be completely unloaded and discharged (if the hydraulic system is maintained and the accumulator 4 needs to be unloaded, this state is entered).

[0064] When the hydraulic system is switched from the high-pressure mode to the low-pressure mode, the accumulator 4 needs to be unloaded first.

[0065] The system also includes an oil tank 1, a hydraulic pump 2, a one-way valve 1 3, a one-way valve 2 13, a one-way valve 3 14, and a filter 12. The solenoid valve 1 6, the solenoid valve 2 7, and the solenoid valve 3 8 are connected in parallel between the hydraulic pump 2 and the hydraulic cylinder 17, and the one-way valve 1 3 is used for unidirectional conduction of the oil circuit that synchronously enters the solenoid valve 2 7 and the solenoid valve 3 8, and the one-way valve 1 3 is also arranged in parallel with the solenoid valve 1 6. An accumulator 4 and a pressure gauge 5 are arranged on the oil circuit that unidirectionally conducts the oil circuit that synchronously enters the solenoid valve 2 7 and the solenoid valve 3 8. The one-way valve 2 13 is used for unidirectional conduction of the oil circuit that enters the oil tank 1, and the oil at the oil circuit receiving end of the one-way valve 2 13 comes from the manual valve 16 when it is in its second working position or from the manual valve 16 when the solenoid valve 3 8 is in its first working position. A solenoid valve 27 in a working position, the oil circuit where the solenoid valve is located is connected in parallel with the one-way valve, which is connected in parallel with the relief valve 19 and the relief valve 210 to perform parallel unloading with the one-way valve 213. There are three groups of one-way valves 314. The first group of one-way valves 314 is used for one-way conduction of the oil circuit from the rod chamber of the hydraulic cylinder 17 to the manual valve 16, and the second group of one-way valves 314 is used for one-way conduction of the oil circuit from the rodless chamber of the hydraulic cylinder 17 to the manual valve 16, and the conducting paths of the first group of one-way valves 314 and the second group of one-way valves 314 are opposite. The throttle valve 15 is connected in the oil circuit flowing from the rodless chamber of the hydraulic cylinder 17 to the relief valve 311 and the solenoid valve 38, and the third group of one-way valves 314 is connected in parallel at both ends of the throttle valve 15, and its conducting path is the same as that of the second group of one-way valves 314.

[0066] The hydraulic system of this embodiment is analyzed as follows in conjunction with the accompanying drawings:

[0067] First compare Figure 1 and Figure 2-7 ;

[0068] Figure 1 The hydraulic system shown is a system that uses a hydraulic cylinder 17 to drive two pressure rollers 19 at the same time; Figure 2-7 The two pressing rollers 19 shown in the figure are driven by two hydraulic cylinders 17 individually, and the only difference is that one hydraulic cylinder 17 is added; if there are three pressing rollers 19 and they are driven by three hydraulic cylinders 17 individually, one more hydraulic cylinder 17 can be added to the hydraulic system;

[0069] It can be combined Figure 2 Observe the oil circuit diagram when the solenoid valve 6 is in the high pressure mode when it is turned on to its first working position. At this time, the working pressure of the hydraulic system can be limited to 250 bar of high pressure through the relief valve 9; Figure 3 Observe the oil circuit diagram when the solenoid valve 1 6 is in the low pressure mode when it is turned on to its second working position. At this time, the working pressure of the hydraulic system can be limited to a low pressure of 60 bar by the relief valve 2 10;

[0070] And can also be combined Figure 4 observe, Figure 4The three states in the position control mode are highlighted with red lines to facilitate observation of the line direction. In this mode, the solenoid valve 27 is in its first working position, and the hydraulic system works in the position control mode. The actions are:

[0071] The solenoid valve 3 8 switches to its second working position, oil enters the rodless chamber of the hydraulic cylinder 17, and the piston rod 18 extends;

[0072] The solenoid valve 3 8 switches to its third working position, oil enters the rod chamber of the hydraulic cylinder 17, the piston rod 18 retracts, and the throttle valve 15 limits the oil return speed of the rodless chamber of the hydraulic cylinder 17, so that the speed of extending and retracting the piston rod 18 is consistent;

[0073] The electromagnetic valve 38 switches to its first working position, the rodless chamber and the rod chamber of the hydraulic cylinder 17 are locked. If material accumulates between the pressure roller 19 and the ring die 20, causing the pressure in the rodless chamber to exceed the set pressure of the relief valve 311, the relief valve 311 is unloaded;

[0074] Then you can combine Figure 5 observe, Figure 5 The state in the force control mode is highlighted with a red line to facilitate observation of the line direction. In this mode, the solenoid valve 2 7 is in its second working position, and the hydraulic system works in the force control mode:

[0075] The thrust of the hydraulic cylinder 17, where is the hydraulic system pressure, and are the effective working areas of the rodless chamber and the rod chamber of the hydraulic cylinder 17, respectively. The accumulator 4 of the hydraulic system can stabilize the pressure of the hydraulic system;

[0076] The accumulator 4 stabilizes the pressure of the hydraulic system, the hydraulic cylinder 17 adaptively adjusts the piston position, and the process system controls the feeding speed according to the displacement of the piston rod 18;

[0077] If the material accumulation between the pressure roller 19 and the ring die 20 increases, the piston rod 18 of the hydraulic cylinder 17 will retract, and the gap between the pressure roller 19 and the ring die will increase, which can prevent the ring die 20 from getting stuck (to reduce the feeding speed and provide time to reduce the material accumulation), and the overflow valve 3 11 limits the safety value of the hydraulic system;

[0078] If the material accumulation between the pressure roller 19 and the ring die 20 is reduced, the piston of the hydraulic cylinder 17 extends, and the gap between the pressure roller 19 and the ring die is reduced (until the pressure roller 19 and the ring die 20 are in direct contact), which can prevent the pressure roller 19 from slipping due to insufficient adhesion;

[0079] If a foreign object enters between the pressure roller 19 and the ring die 20, the piston of the hydraulic cylinder 17 is forced to retract: if the piston is forced to retract and the hydraulic system pressure exceeds the set pressure of the relief valve 3 11, the relief valve 3 11 is unloaded; and it can be judged whether a foreign object has entered the pressure roller 19 according to the change in the displacement of the piston of the hydraulic cylinder 17;

[0080] Then you can combine Figure 6-7 Observe that when the manual valve 16 works in its second working position, the hydraulic system is unloaded:

[0081] If the solenoid valve is working in the first working position, only the hydraulic cylinder 17 is unloaded;

[0082] If the solenoid valve 3 works in its second working position or the third working position, the accumulator 4 and the hydraulic cylinder 17 are both unloaded.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A ring die pelletizing machine roller die gap adaptive force control hydraulic system, characterized in that: It has two working modes: position control mode and force control mode. It can automatically adjust the gap between the pressure roller and the ring die through the hydraulic cylinder.

2. The ring die pelletizing machine roller die gap adaptive force control hydraulic system according to claim 1, characterized in that: The system also has a switching mode between high pressure and low pressure, and the switching between the high pressure mode and the low pressure mode is performed through solenoid valve 1. When solenoid valve 1 is switched to its first working position, overflow valve 1 is turned on, and overflow valve 1 is used to prevent system overload in high pressure mode. When solenoid valve 1 is switched to its second working position, overflow valve 2 is turned on, and overflow valve 2 is used to prevent system overload in low pressure mode.

3. The ring die pelletizing machine roller die gap adaptive force control hydraulic system according to claim 2, characterized in that: The position control mode and the force control mode are switched between two positions through solenoid valve 2. When solenoid valve 2 is switched to its first working position, the system is in the position control mode, and when solenoid valve 2 is switched to its second working position, the system is in the force control mode.

4. The ring die pelletizing machine roller die gap adaptive force control hydraulic system according to claim 3, characterized in that: In the position control mode, the system adjusts the working state of the hydraulic cylinder through solenoid valve three to adjust the gap between the pressure roller and the ring die. When the solenoid valve three is switched to its second working position, oil enters the rodless chamber of the hydraulic cylinder and the piston rod extends. When the solenoid valve three is switched to its third working position, oil enters the rod chamber of the hydraulic cylinder and the piston rod retracts. The throttle valve in the system oil circuit is used to limit the oil return speed of the rodless chamber of the hydraulic cylinder to make the extension and retraction speed of the piston rod consistent. When the solenoid valve three is switched to its first working position, the rodless chamber and the rod chamber of the hydraulic cylinder are locked.

5. The ring die pelletizing machine roller die gap adaptive force control hydraulic system according to claim 4, characterized in that: A relief valve 3 is also installed on the oil return line of the rodless chamber of the hydraulic cylinder. During the operation of the system, if a hard object enters between the pressure roller and the ring die, causing the pressure of the hydraulic system to exceed the set pressure of the relief valve 3, the relief valve 3 will unload and the piston rod of the hydraulic cylinder will retract, thereby avoiding damage to the pressure roller or the ring die.

6. The ring die pelletizing machine roller die gap adaptive force control hydraulic system according to claim 4, characterized in that: In the force control mode, the oil circuits of the rodless chamber and the rod chamber of the hydraulic cylinder are connected, the thrust of the hydraulic cylinder is determined by the hydraulic system pressure and the working area of ​​the hydraulic cylinder, the accumulator is used to stabilize the hydraulic system pressure, and the displacement of the hydraulic cylinder piston rod is used to reflect the material accumulation condition between the pressure roller and the ring die and control the feeding speed.

7. A ring die pelletizing machine roller die gap adaptive force control hydraulic system according to claim 6, characterized in that: In the force control mode, the solenoid valve three is only in its second working position or the third working position.

8. The ring die pelletizing machine roller die gap adaptive force control hydraulic system according to claim 6, characterized in that: The system also has an unloading mode. In both the position control mode and the force control mode, the manual valve is in its first working position, and in the unloading mode, the manual valve is in its second working position. At the same time, when the solenoid valve three is in its first working position, only the hydraulic cylinder is unloaded, and when the solenoid valve three is in its second working position or its third working position, the accumulator and the hydraulic cylinder are unloaded at the same time.

9. The ring die pelletizing machine roller die gap adaptive force control hydraulic system according to claim 8, characterized in that: When switching the hydraulic system from high pressure mode to low pressure mode, the accumulator must be unloaded first.

10. The ring die pelletizing machine roller die gap adaptive force control hydraulic system according to claim 8, characterized in that: It also includes an oil tank, a hydraulic pump, a one-way valve 1, a one-way valve 2, a one-way valve 3, and a filter. The solenoid valve 1, the solenoid valve 2, and the solenoid valve 3 are connected in parallel between the hydraulic pump and the hydraulic cylinder, and the one-way valve 1 is used for unidirectional conduction of the oil circuit that synchronously enters the solenoid valve 2 and the solenoid valve 3, and the one-way valve 1 is also arranged in parallel with the solenoid valve 1. An accumulator and a pressure gauge are arranged on the one-way valve 1 unidirectional conduction of the oil circuit that synchronously enters the solenoid valve 2 and the solenoid valve 3. The one-way valve 2 is used for unidirectional conduction of the oil circuit that enters the oil tank, and the oil at the oil circuit receiving end of the one-way valve 2 comes from the manual valve when it is in its second working position or from the solenoid valve 3 when it is in its first working position. The solenoid valve two in the first working position, the oil circuit where the solenoid valve is located is connected in parallel with the one-way valve, which is connected in parallel with the overflow valve one and the overflow valve two to perform parallel unloading with the one-way valve two, the one-way valve three is provided with three groups, the first group of one-way valve three is used for one-way conduction of the oil circuit from the rod chamber of the hydraulic cylinder into the manual valve, the second group of one-way valve three is used for one-way conduction of the oil circuit from the rodless chamber of the hydraulic cylinder into the manual valve, and the conducting paths of the first group of one-way valve three and the second group of one-way valve three are opposite, the throttle valve is connected in the oil circuit flowing from the rodless chamber of the hydraulic cylinder to the overflow valve three and the solenoid valve three, and the third group of one-way valve three is connected in parallel at both ends of the throttle valve, and it has the same conducting path as the second group of one-way valve three.

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