Servo-driven hydraulic grab bucket system and grab bucket for large-scale crane

Abstract

The application discloses a servo drive hydraulic grab bucket system and grab bucket for a large crane and belongs to the technical field of cranes. The servo drive hydraulic grab bucket system for the large crane comprises an oil tank for storing hydraulic oil and a hydraulic control system, the oil tank is communicated with the hydraulic control system through a hydraulic pipeline and forms a closed circulating oil path, and the hydraulic control system comprises: a hydraulic cylinder body connected with the grab bucket; a hydraulic pump group composed of a constant-power variable pump driven by a servo motor, an oil inlet of the hydraulic pump group being connected with the oil tank through the hydraulic pipeline and an oil outlet of the hydraulic pump group being connected with a hydraulic pump head valve group; and the hydraulic pump head valve group comprising an electromagnetic ball valve, an input end of the electromagnetic ball valve being connected with an output end of the hydraulic pump group and an output end of the electromagnetic ball valve being connected with an oil inlet of a control valve group. The servo drive hydraulic system is utilized to realize linear and continuous change of the working speed of the super-large grab bucket through double-variable control, and the stability, working life and working efficiency of the working system are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of crane technology, and more particularly to a servo-driven hydraulic grab system and grab for large cranes. Background Technology

[0002] Hydraulic grabs are playing an increasingly important role in actual production, such as in the field of waterway dredging technology, due to their advantages such as fast response and high efficiency. The main movements of hydraulic grabs rely on hydraulic cylinders, and most hydraulic grabs used for load lifting on large cranes need to be equipped with hydraulic systems to realize the movement of hydraulic cylinders.

[0003] Currently, ultra-large grab buckets used in waterway dredging employ traditional hydraulic control systems. These systems primarily control the working speed of the ultra-large grab bucket by adjusting the number of working pumps and the differential operation of the working cylinders. Therefore, the working speed of the ultra-large grab bucket exhibits a step-like change. The speed control of the ultra-large grab bucket is based on changes in oil flow rate. Sudden surges and drops in flow rate can easily cause problems such as pipeline vibration, pressure overshoot, pressure oscillation, and hydraulic shock in the hydraulic system, leading to increased system failure rate, reduced service life of hydraulic components, and affecting the use of hydraulic cylinders. Summary of the Invention

[0004] The purpose of this invention is to solve the problems existing in the prior art, and to propose a servo-driven hydraulic grab system and grab for large cranes.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A servo-driven hydraulic grab system for a large crane includes an oil tank for storing hydraulic oil and a hydraulic control system. The oil tank is connected to the hydraulic control system via hydraulic pipelines to form a closed-loop oil circuit. The hydraulic control system includes:

[0007] Hydraulic cylinder body, which is connected to the grab bucket;

[0008] The hydraulic pump unit consists of a constant power variable pump driven by a servo motor. Its oil inlet is connected to the oil tank through a hydraulic pipeline, and its oil outlet is connected to the hydraulic pump head valve group.

[0009] The hydraulic pump head valve assembly includes a solenoid ball valve, the input end of which is connected to the output end of the hydraulic pump assembly, and the output end is connected to the oil inlet of the control valve assembly.

[0010] The control valve assembly has its inlet connected to the hydraulic pump head valve assembly, and its working ports connected to the rodless chamber and rod chamber of the hydraulic cylinder body, respectively. The rodless chamber of the hydraulic cylinder body is connected to the rodless chamber oil circuit of the control valve assembly through a hydraulic pipeline, and the rod chamber of the hydraulic cylinder body is connected to the rod chamber oil circuit of the control valve assembly.

[0011] The servo motor and the constant power variable pump are rigidly connected by a coupling.

[0012] Preferably, the hydraulic pump group includes multiple uniformly distributed constant power high-pressure piston variable pumps, the variable pumps are coaxially connected to the servo motor, and the pump outlets are connected in parallel to the hydraulic pump head valve group through hydraulic pipelines.

[0013] Preferably, the control valve assembly includes:

[0014] The rodless chamber inlet valve assembly and the rod chamber inlet valve assembly of the hydraulic cylinder;

[0015] Hydraulic cylinder rodless chamber return valve assembly and rod chamber return valve assembly;

[0016] The differential valve assembly is connected between the rodless chamber and the rod chamber to form a differential control loop to drive the piston rod to move by utilizing the area difference between the two ends of the piston.

[0017] The pressure relief valve assembly is connected in parallel between the rodless chamber oil circuit and the oil tank;

[0018] The safety valve is connected in series at the end of the main oil circuit, and its overflow port is directly connected to the oil tank.

[0019] Preferably, in the control valve assembly:

[0020] The rodless chamber inlet valve group and the rod chamber inlet valve group are connected in parallel in the main oil circuit. The inlets of both are connected to the output end of the hydraulic pump head valve group, and the outlets are connected to the rodless chamber and the rod chamber of the hydraulic cylinder body through hydraulic pipelines, respectively.

[0021] The solenoid valve of the differential valve group of the control valve group is a three-position four-way valve. Its port A is connected to the inlet of the rodless chamber oil inlet valve group, and its port B is connected to the outlet of the rod chamber oil return valve group, forming a diagonal connection structure of the differential oil circuit.

[0022] Preferably, the hydraulic cylinder body includes:

[0023] The cylinder block and piston rod are connected in a sliding manner.

[0024] The hinge seat has two ends that are respectively connected to the cylinder body and the piston rod. The hinge seat at the piston rod end has a recessed hole for connecting to the hydraulic grab bucket.

[0025] The protective cover is slidably sleeved on the outside of the cylinder and linked with the piston rod. Its side wall is provided with a strip groove that cooperates with the hydraulic pipeline on the outside of the cylinder.

[0026] And a shielding component to dynamically close the strip groove.

[0027] Preferably, the protective cover includes:

[0028] The protective tube slides in conjunction with the cylinder block;

[0029] The hinge plate is fixed to the end of the protective tube and is connected to the hinge seat at the end of the piston rod by a pin.

[0030] The strip-shaped groove extends axially along the protective tube, and a first opening is provided on the side near the hinge seat connected to the cylinder body.

[0031] Preferably, the shading component includes:

[0032] Arc-shaped grooves are symmetrically formed on the inner walls of both sides of the strip-shaped groove;

[0033] Multiple arc-shaped baffles are provided and are slidably embedded in the arc-shaped grooves side by side;

[0034] An elastic element is disposed between the arc-shaped baffle and the arc-shaped groove;

[0035] Among them, the arc-shaped baffles on the same vertical plane in the arc-shaped grooves on both sides move and abut against each other.

[0036] Preferably, the protective pipe is provided with a guide plate at the outer hydraulic line, and each of the arc-shaped baffles is provided with a force-bearing plate at the bottom that moves against the guide plate. Both the guide plate and the force-bearing plate are provided with matching extrusion slopes.

[0037] Preferably, the protective tube has a second opening at the end furthest from the cylinder body, and an annular groove is formed at the second opening, with the following circumferentially distributed within the annular groove:

[0038] Support plate assembly, each support plate assembly consists of two support plates arranged in pairs;

[0039] A rotating shaft mounted between two support plates;

[0040] A movable plate is connected to the outside of the rotating shaft by a torsion spring and moves against the inner wall of the annular groove;

[0041] A brush fixed to the end of the movable plate;

[0042] The brush maintains elastic contact with the piston rod surface.

[0043] The present invention also discloses a grab bucket applicable to the aforementioned servo-driven hydraulic grab bucket system for large cranes, comprising a bucket base connected to the crane's wire rope and two bucket bodies hinged to the bucket base, wherein the bucket bodies are connected to the piston rod of a hydraulic cylinder body, and the opening and closing of the bucket bodies is driven by the hydraulic cylinder body controlled by the hydraulic control system.

[0044] Compared with the prior art, the present invention provides a servo-driven hydraulic grab system and grab for large cranes, which has the following advantages:

[0045] 1. The servo-driven hydraulic grab system and grab for large cranes, by moving the piston rod out of the cylinder body, causes the protective cover to slide on the cylinder body, so that the protective cover protects the piston rod that has moved out of the cylinder body, and avoids damage and deformation of the piston rod due to collision with external materials when the hydraulic cylinder controls the grab to perform dredging operations, thereby ensuring the service life of the hydraulic cylinder.

[0046] 2. The servo-driven hydraulic grab system and grab for large cranes, by opening a strip groove on the protective tube, allows the protective tube to automatically adapt to the hydraulic lines outside the cylinder body when moving relative to the cylinder body, avoiding collision between the protective tube and the hydraulic lines. After the protective tube moves away from the hydraulic lines, the arc-shaped baffle on the protective tube is reset and moved under the push of the compressed elastic element, so that the arc-shaped baffle blocks the strip groove, preventing the piston rod from being exposed due to the strip groove, thereby ensuring the protection effect on the piston rod and further improving the protection capability of the hydraulic cylinder.

[0047] 3. The servo-driven hydraulic grab system and grab for large cranes, by elastically setting a movable plate at one end of the protective tube, allows the movable plate to be in a closed state when the piston rod moves out of the cylinder, preventing external materials from colliding with the piston rod from the opening. When the piston rod retracts into the cylinder, the material entering between the protective tube and the piston rod will have its internal space reduced as the piston rod retracts. The water or material entering will automatically exert a force on the movable plate on the lower side under its own gravity and pushing force, causing the movable plate to flip relative to the protective tube, thus removing the water or debris that has entered into the protective tube. This prevents debris from accumulating in the protective tube as the piston rod retracts into the cylinder, which would affect the retraction action of the piston rod.

[0048] 4. This servo-driven hydraulic grab system and grab for large cranes uses a servo motor to control the speed of a constant-power variable pump, which outputs high-pressure oil at different flow rates. The high-pressure oil output by the constant-power variable pump forces the piston of the hydraulic cylinder to move, thereby achieving position control of the ultra-large grab. The dual variable control of the servo motor and the variable pump makes the working speed of the ultra-large grab change linearly and continuously, reducing the vibration generated by the ultra-large grab during operation, reducing the hydraulic shock of the servo-driven hydraulic system, improving the smoothness of the ultra-large grab's movement, and effectively improving the stability, service life, and working efficiency of the working system. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the external structure of the hydraulic cylinder of the present invention. Figure 1 ;

[0050] Figure 2 This is a schematic diagram of the external structure of the hydraulic cylinder of the present invention. Figure 2 ;

[0051] Figure 3This is a schematic diagram of the structure of the hydraulic cylinder of the present invention;

[0052] Figure 4 This is a schematic diagram of the structure of the end of the protective cover of the present invention;

[0053] Figure 5 This is a cross-sectional structural diagram of the protective tube of the present invention;

[0054] Figure 6 This is a schematic diagram of the external structure of the arc-shaped baffle of the present invention;

[0055] Figure 7 This is a schematic diagram of the internal structure of the annular groove of the present invention;

[0056] Figure 8 Hydraulic schematic diagram for a servo-driven hydraulic control system;

[0057] Figure 9 Hydraulic schematic diagram of the control valve assembly;

[0058] Figure 10 A schematic diagram of the motion curve of an ultra-large grab bucket;

[0059] Figure 11 A schematic diagram of the simulation curve of the piston rod motion speed in a servo-driven hydraulic system;

[0060] Figure 12 A schematic diagram of the simulation curve of the piston rod movement speed in a traditional hydraulic system;

[0061] Figure 13 for Figure 8 A schematic diagram of the enlarged middle section.

[0062] In the diagram: 1. Oil tank; 2. Hydraulic pump assembly; 3. Hydraulic pump head valve assembly; 4. Control valve assembly; 401. Rodless chamber inlet valve assembly; 402. Rod chamber inlet valve assembly; 403. Rod chamber return valve assembly; 404. Rodless chamber return valve assembly; 405. Differential valve assembly; 406. Pressure relief valve assembly; 407. Safety valve; 5. Hydraulic cylinder body; 501. Cylinder body; 502. Piston rod; 6. Hydraulic pipeline; 7. Protective cover; 701. Protective pipe; 7011. Strip groove; 702. Hinge plate; 8. Arc groove; 801. Arc baffle; 802. Elastic element; 9. Guide plate; 10. Force plate; 11. Annular groove; 111. Support plate; 112. Rotating shaft; 113. Movable plate; 114. Brush; 12. Hinge seat; 121. Concave hole. Detailed Implementation

[0063] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0064] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0065] like Figures 8 to 13 As shown, this embodiment proposes a servo-driven hydraulic grab system for large cranes. The servo-driven hydraulic system consists of an oil tank 1, a hydraulic pump group 2, a hydraulic pump head valve group 3, a control valve group 4, a hydraulic cylinder body 5, and hydraulic pipelines 6. The hydraulic pump group 2 is equipped with a constant power high-pressure plunger variable pump to power the hydraulic cylinder body 5. The pumps are evenly distributed to ensure the balance of the ultra-large grab during operation. The oil in the oil tank 1 is pumped into the servo-driven hydraulic system through the hydraulic pipelines 6 and the hydraulic pump group 2. The constant power variable pump outlet of the hydraulic pump group 2 is equipped with a pressure detection interface. The pressure sensor monitors the system pressure in real time through the pressure detection interface and is connected to the servo motor controller. The high-pressure oil enters the hydraulic pump head valve group 3, and the solenoid ball valve of the hydraulic pump head valve group 3 is energized to form a passage. Then, the high-pressure oil passes through the control valve group 4 to the rodless chamber of the hydraulic cylinder body 5. The low-pressure oil in the rod chamber of the hydraulic cylinder flows back to the oil tank 1 through the control valve group 4. The piston rod 502 of the hydraulic cylinder body 5 extends, and the ultra-large grab closes.

[0066] Under low load operation, the control valve group 4 is equipped with a valve group to control the connecting oil circuit from the rod chamber to the rodless chamber. By utilizing the resultant force difference formed by the difference in the area of ​​the piston at both ends inside the hydraulic cylinder body 5, the piston rod 502 of the hydraulic cylinder body 5 is pushed to move, and the ultra-large grab bucket achieves differential high-speed bucket closing.

[0067] Then the control valve group 4 forms a circuit break, and the oil remains in the rod chamber and rodless chamber of the hydraulic cylinder body 5. The piston rod 502 of the hydraulic cylinder body 5 maintains its position, realizing the pressure holding of the servo-driven hydraulic grab system used for large cranes.

[0068] The pressure is unloaded in the rodless chamber of the hydraulic cylinder body 5 by controlling valve group 4, and the rod chamber is connected to high-pressure oil. The resultant force difference at both ends of the piston causes the piston rod 502 of the hydraulic cylinder body 5 to retract, and the super-large grab bucket is opened.

[0069] In traditional examples, the grab bucket servo drive hydraulic system uses a stepper motor to control the working pump. The working speed of the grab bucket is controlled by adjusting the number of working pumps and the differential of the working cylinder. The flow rate changes significantly, which leads to large changes in the acceleration of the piston rod 502 during the execution of the working cylinder, resulting in significant impact during operation. Figure 10 This is a schematic diagram of the motion curve of the ultra-large grab bucket in this application. See also the comparison with traditional examples. Figure 11 and Figure 12 The servo-driven hydraulic grab system for large cranes proposed in this invention features linear flow rate variation, enabling the piston rod 502 to reciprocate. The piston rod 502 exhibits minimal acceleration and deceleration variations, resulting in stable motion characteristics of the working cylinder. Under the same operating conditions, the servo-driven electro-hydraulic control system has a shorter working cycle and higher efficiency.

[0070] The servo-driven hydraulic system of this invention enables dynamic response to the movement of ultra-large grab buckets. The dual variable control of the servo motor and variable pump improves work efficiency, reduces the vibration generated by the ultra-large grab buckets during operation, reduces hydraulic shock in the servo-driven hydraulic system, improves the stability of the movement of ultra-large grab buckets, and extends the service life of the system.

[0071] like Figure 8 and Figure 9 As shown, in a preferred embodiment, based on the above method, the hydraulic pump group 2 further includes multiple uniformly distributed constant power high-pressure piston variable pumps. The variable pumps are coaxially connected to the servo motor, and the servo motor and the constant power variable pumps are rigidly connected through a coupling. The pump outlet is connected in parallel to the hydraulic pump head valve group 3 through the hydraulic pipeline 6.

[0072] like Figure 8 and Figure 9 As shown, in a preferred embodiment, based on the above method, the control valve group 4 is further composed of multiple parts, namely, the hydraulic cylinder rodless chamber oil inlet valve group 401, the hydraulic cylinder rod chamber oil inlet valve group 402, the hydraulic cylinder rod chamber oil return valve group 403, the hydraulic cylinder rodless chamber oil return valve group 404, the differential valve group 405, the pressure relief valve group 406, and the safety valve 407.

[0073] In the control valve group 4: the rodless chamber oil inlet valve group 401 and the rod chamber oil inlet valve group 402 are connected in parallel in the main oil circuit to realize independent oil supply control of the two chambers of the hydraulic cylinder body 5 and avoid action interference. The inlets of both are connected to the output end of the hydraulic pump head valve group 3, and the outlets are connected to the rodless chamber and the rod chamber of the hydraulic cylinder body 5 respectively through the hydraulic pipeline 6.

[0074] The P port of the differential valve group 405 is connected to the outlet of the rod chamber return valve group 403, and the T port is connected to the inlet of the rodless chamber inlet valve group 401, forming a diagonal connection structure of the differential oil circuit; the pressure relief valve group 406 is set in parallel between the rodless chamber oil circuit and the oil tank 1, and its opening pressure threshold is 110% of the rated pressure of the system, reducing the system pressure shock through bypass pressure relief; the safety valve 407 is connected in series at the end of the main oil circuit, and its overflow port is directly connected to the oil tank 1. When the system pressure exceeds the threshold, it directly relieves pressure to the oil tank 1, forming a dual protection mechanism with the pressure relief valve group 406; the differential valve group 405 is a three-position four-way solenoid directional valve, which connects the rodless chamber and the rod chamber oil circuit in the middle position during the closed stage, forming a differential speed-increasing circuit; a double cooler is set between the outlet of the rod chamber return valve group 403 and the oil tank 1, and its cooling medium channel is arranged in counterflow with the rod chamber return oil pipeline of the hydraulic cylinder body 5.

[0075] like Figures 1 to 4 As shown, in a preferred embodiment, based on the above method, the hydraulic cylinder body 5 is further composed of a cylinder body 501 and a piston rod 502 that are slidably connected. The cylinder body 501 and the piston rod 502 form a dynamic seal. A hinge seat 12 is provided at the ends of the cylinder body 501 and the piston rod 502 that are far apart from each other. The bidirectional force transmission of the grab bucket is realized through the hinge seat 12. The design of the concave hole 121 improves the connection stability. The strip groove 7011 of the protective cover 7 dynamically cooperates with the hydraulic pipeline 6 to solve the problem of interference with the external pipeline of the traditional oil cylinder. The shielding component simultaneously realizes pipeline avoidance and piston rod 502 sealing, achieving the technical effect of "dynamic sealing" of the strip groove 7011.

[0076] like Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, in a preferred embodiment, based on the above method, the protective cover 7 further includes a protective tube 701 that slides with the cylinder body 501 and a hinge plate 702 fixed to the end of the protective tube 701. The hinge plate 702 is connected to the hinge seat 12 to ensure that the movement trajectory of the protective tube 701 and the piston rod 502 is synchronized. It should be noted that the end of the strip groove 7011 away from the piston rod 502 has a first opening to ensure that the protective cover 7 moves away from the cylinder body 501 as the piston rod 502 moves away from the cylinder body 501. One end is not obstructed by the hydraulic line 6 connected to the cylinder body 501, ensuring that the protective cover 7 slides smoothly. The protective cover 7 protects the piston rod 502 that has moved out of the cylinder body 501, preventing the piston rod 502 from being damaged or deformed by external materials when the hydraulic cylinder controls the grab bucket to perform dredging operations, thereby ensuring the service life of the hydraulic cylinder. In addition, ball bearings can be installed on the inner wall of the protective tube 701 to abut against the cylinder body 501, so that sliding friction is converted into rolling friction, reducing the wear during displacement and ensuring the service life of the hydraulic cylinder.

[0077] like Figure 4 , Figure 5 and Figure 6 As shown, in a preferred embodiment, based on the above method, the shielding component further includes multiple arc-shaped baffles 801 that slide within the arc-shaped groove 8 under elastic force, the multiple arc-shaped baffles 801 forming a "fish scale" sealing surface, and the elastic element 802 providing a constant clamping force.

[0078] Furthermore, a guide plate 9 is provided at the outer hydraulic line 6 of the protective pipe 701, and a force-bearing plate 10 is provided at the bottom of each arc-shaped baffle 801 to move against the guide plate 9; when the piston rod 502 moves out of the cylinder body 501, the force-bearing plate 10 no longer abuts against the guide plate 9, and the arc-shaped baffle 801 connected to the force-bearing plate 10 is reset under the push of the elastic element 802, realizing the dynamic sealing of the strip groove 7011, so that the arc-shaped baffle 801 blocks the strip groove 7011, preventing the protective pipe 701 from exposing the piston rod 502 due to the strip groove 7011, thereby ensuring the protective effect on the piston rod 502 and further improving the protection capability of the hydraulic cylinder;

[0079] When the piston rod 502 retracts into the cylinder 501, the force plate 10 abuts against the guide plate 9 fixed on the outside of the cylinder 501. The force plate 10 is subjected to force and drives the arc-shaped baffle 801 away, avoiding the hydraulic pipeline 6 connected to the outside of the cylinder 501.

[0080] like Figure 4 and Figure 7 As shown, in a preferred embodiment, based on the above method, a second opening is provided at the end of the protective pipe 701 away from the cylinder 501 to facilitate the smooth discharge of water or materials entering through the strip groove 7011. An annular groove 11 is formed at the second opening, and multiple movable plates 113 are arranged circumferentially outside the support plate 111 within the annular groove 11. The movable plates 113 are automatically opened and closed by torsion springs. When the protective pipe 701 is away from the cylinder 501, the movable plates 113 are closed relative to the second opening, preventing external materials from impacting the piston rod 5 through the second opening. 02 Collision: When the piston rod 502 retracts into the cylinder 501, the material entering between the protective tube 701 and the piston rod 502 will shrink as the piston rod 502 retracts. The water or material entering will automatically exert a force on the movable plate 113 located below under its own gravity and pushing force, causing the movable plate 113 to flip relative to the rotating shaft 112, so that the water or debris entering the protective tube 701 will be automatically removed, thus preventing debris from accumulating in the protective tube 701 as the piston rod 502 retracts into the cylinder 501, which would affect the retraction action of the piston rod 502.

[0081] It should be noted that the brush 114 contacts the piston rod 502, which can both scrape off impurities and maintain the oil film, further solving the problem of debris accumulation on the outside of the piston rod 502.

[0082] The present invention also discloses a grab bucket applicable to the aforementioned servo-driven hydraulic grab bucket system for large cranes, comprising a bucket base connected to the crane's wire rope and two bucket bodies hinged to the bucket base. The bucket bodies are connected to the piston rod 502 of the hydraulic cylinder body 5. The bucket bodies are existing technology and will not be described in detail here. The opening and closing of the bucket bodies are driven by the hydraulic cylinder body 5 controlled by the hydraulic control system.

[0083] The working method of the hydraulic control system is specifically implemented as follows:

[0084] The servo-driven hydraulic control system proposed in this invention controls the opening, grabbing, and closing postures of the ultra-large grab bucket. Based on the working conditions of the ultra-large grab bucket, the system comprises three stages: bucket closing, pressure holding, and bucket opening. The specific working process is as follows:

[0085] I. Closed-off Phase

[0086] When the servo-driven hydraulic system receives the bucket closing signal, the super-large grab bucket begins to close. The bucket closing process is divided into four stages: low-speed bucket closing, differential speed increase activation, differential speed increase deactivation, and deceleration bucket closing.

[0087] During the low-speed closing phase, hydraulic fluid is delivered through hydraulic pipeline 6. Hydraulic pump group 2 draws high-pressure hydraulic fluid from oil tank 1. The high-pressure hydraulic fluid passes through hydraulic pump head valve group 3. All solenoid valves of hydraulic pump head valve group 3 are energized and opened. Hydraulic pump head valve group 3 controls the direction of hydraulic fluid movement and plays a safety protection role. The high-pressure hydraulic fluid enters control valve group 4 through hydraulic pump head valve group 3. The solenoid valve of hydraulic cylinder rodless chamber inlet valve group 401 is energized and opened to form a passage. Among them, safety valve 407 in control valve group 4 is a relief valve, which controls the hydraulic fluid pressure in the pipeline to prevent pipeline pressure overload. The high-pressure hydraulic fluid flows through control valve group 4 into the rodless chamber of hydraulic cylinder body 5. The high-pressure oil acts on the piston of hydraulic cylinder body 5, forcing the piston to move to the right and causing piston rod 502 to extend. The ultra-large grab bucket achieves low-speed closing.

[0088] During the closed-loop operation, when the system pressure is below the critical point of the constant-power variable pump's operating characteristic curve, the constant-power variable pump in hydraulic pump group 2 outputs at less than full power, with the constant-power variable pump outputting at its maximum displacement Vgmax. The servo motor increases the speed to regulate the displacement of the constant-power variable pump. Compared with traditional examples, this effectively addresses the wasted power of the motor when the hydraulic pump is not outputting at full power, thereby improving the displacement of the variable pump and the working efficiency of the ultra-large grab bucket. When the system pressure is above the critical point of the constant-power variable pump's operating characteristic curve, the variable pump outputs at full power. Based on the constant-power characteristic of the variable pump, the output displacement is inversely proportional to the system pressure. As the variable pump displacement changes from Vgmax to Vgmin, the system pressure increases.

[0089] The servo-driven hydraulic system pressure sensor detects the system pressure. When the system pressure is lower than the rated value, the differential speed-increasing circuit of the differential valve group 405 automatically opens, increasing the closing speed of the ultra-large grab bucket. During the differential speed-increasing phase, the solenoid valve of the differential valve group 405 in the control valve group 4 is energized, forming a passage. The rodless chamber and the rod chamber of the hydraulic cylinder body 5 are connected, and the pressure on both sides of the piston tends to be balanced. Due to the different oil action areas on both sides of the piston, the resultant force in the rodless chamber is greater than that in the rod chamber. Utilizing the resultant force difference formed by the area difference at both ends of the piston, the piston rod 502 of the hydraulic cylinder body 5 is driven to move at an increased speed, and the ultra-large grab bucket achieves differential closing.

[0090] The pressure sensor in the servo-driven hydraulic system detects the system pressure. If the system pressure exceeds the rated value, the differential speed-up circuit closes. With the differential speed-up closed, the solenoid valve of differential valve group 405 is de-energized, creating an open circuit, and the extra-large grab bucket achieves differential release. During this stage, the system pressure is still higher than the critical point of the constant power variable pump's operating characteristic curve, and the variable pump continues to output full power, resulting in high working efficiency, low energy loss, and stable and reliable operation of the servo-driven hydraulic system.

[0091] During the closing process of the ultra-large grab bucket, a deceleration action is performed in advance when the distance to the closing end point is detected to prevent impact during the rapid closing stroke of the grab bucket and pressure overshoot of the servo drive hydraulic system. During the deceleration and closing stage, the solenoid valve of the hydraulic pump head valve group 3 is energized to form an open circuit, the solenoid valve of the rodless chamber oil inlet valve group 401 of the hydraulic cylinder is de-energized to form a closed circuit, and the solenoid valve of the rod chamber oil return valve group 403 of the hydraulic cylinder is energized to form an open circuit. The oil returns from the rod chamber of the hydraulic cylinder body 5 to the oil tank 1, and the ultra-large grab bucket achieves deceleration and closing.

[0092] II. Pressure Holding Stage

[0093] During the pressure-holding phase of the ultra-large grab bucket, the solenoid valve of hydraulic pump head valve group 3 is energized to open the system for unloading, and hydraulic pump group 2 does not perform external work. At the same time, the servo motor speed is reduced to the minimum speed Vgmin of the constant power variable pump to achieve energy saving. The solenoid valves in control valve group 4 are all de-energized to form an open circuit, and the oil remains in the rod chamber and rodless chamber of hydraulic cylinder body 5. The piston rod 502 of hydraulic cylinder body 5 maintains its position, which is used to achieve pressure holding in the servo-driven hydraulic grab bucket system of large cranes.

[0094] III. The Beginning of the Battle:

[0095] When the servo-driven hydraulic system receives the bucket opening signal, the super-large grab bucket is ready to open. The bucket opening process is divided into six stages: pressure relief, low-speed bucket opening, full-speed bucket opening, two-stage deceleration bucket opening, and bucket opening stop.

[0096] Before the ultra-large grab bucket opens, pressure is released. After the ultra-large grab bucket closes, the pressure in the rodless chamber of the hydraulic cylinder body 5 rises to the maximum critical value, thus requiring pressure release of the rodless chamber of the hydraulic cylinder body 5. This is achieved by creating a passage through the pressure relief valve group 406 in the control valve group 4, releasing the energy of the high-pressure oil. This reduces the energy impact of the high-pressure oil on the hydraulic lines 6, hydraulic components, and servo-driven hydraulic system, weakens vibration and its noise, and increases the service life of the servo-driven hydraulic system.

[0097] Upon receiving the opening command, the servo-driven hydraulic system, in the low-speed opening phase of the super-large grab bucket, activates the working pump section of hydraulic pump unit 2 to generate high-pressure oil. Oil is drawn from oil tank 1 and transported via hydraulic pipeline 6. The high-pressure oil passes through hydraulic pump head valve group 3, and then through control valve group 4. The solenoid valves of hydraulic cylinder rod chamber inlet valve group 402 and hydraulic cylinder rodless chamber return valve group 404 are energized to form a circuit. Hydraulic cylinder rod chamber inlet valve group 402 delivers high-pressure oil to the rod chamber of hydraulic cylinder body 5 via hydraulic pipeline 6, while hydraulic cylinder rodless chamber return valve group 404 delivers low-pressure oil to oil tank 1 via hydraulic pipeline 6. The piston rod 502 of hydraulic cylinder body 5 is forced to move to the left by the resultant force difference formed by the difference in area at both ends of the piston, causing piston rod 502 to retract, thus achieving low-speed opening of the super-large grab bucket.

[0098] When the super-large grab bucket opens to a certain angle, the servo-driven hydraulic system controls the super-large grab bucket to open at full speed. All working pumps of hydraulic pump group 2 are turned on, and the solenoid valves of hydraulic pump head valve group 3 are energized to form an open circuit, increasing the inlet flow of high-pressure oil. Then, the high-pressure oil flows through the rod chamber inlet valve group 402 of the hydraulic cylinder and is delivered to the rod chamber of the hydraulic cylinder body 5, so that the super-large grab bucket can open at full speed.

[0099] As the super-large grab bucket opens to near its maximum opening point, the number of working pumps in hydraulic pump group 2 is gradually reduced in advance to decelerate the opening of the super-large grab bucket, preventing the impact and vibration caused by the sudden stop of the super-large grab bucket from high-speed operation. The servo-driven hydraulic system is equipped with two stages of deceleration opening to transition from the high-speed opening state to the stop state, enabling the super-large grab bucket to achieve deceleration opening and opening stop.

[0100] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A servo-driven hydraulic grab system for a large crane, comprising an oil tank (1) for storing hydraulic oil and a hydraulic control system, wherein the oil tank (1) is connected to the hydraulic control system via a hydraulic pipeline (6) to form a closed-loop oil circuit, characterized in that, The hydraulic control system includes: Hydraulic cylinder body (5), which is connected to the grab bucket; The hydraulic pump group (2) is composed of a constant power variable pump driven by a servo motor. Its oil inlet is connected to the oil tank (1) through a hydraulic pipeline (6), and its oil outlet is connected to the hydraulic pump head valve group (3). The hydraulic pump head valve group (3) includes a solenoid ball valve, whose input end is connected to the output end of the hydraulic pump group (2) and whose output end is connected to the oil inlet of the control valve group (4); The control valve group (4) has its oil inlet connected to the hydraulic pump head valve group (3), and its working oil inlet connected to the rodless chamber and rod chamber of the hydraulic cylinder body (5) respectively. The rodless chamber of the hydraulic cylinder body (5) is connected to the rodless chamber oil circuit of the control valve group (4) through the hydraulic pipeline (6), and the rod chamber of the hydraulic cylinder body (5) is connected to the rod chamber oil circuit of the control valve group (4). The servo motor and the constant power variable pump are rigidly connected by a coupling. The hydraulic cylinder body (5) includes: The cylinder (501) and piston rod (502) are connected in a sliding manner; The protective cover (7) is slidably sleeved on the outside of the cylinder body (501) and linked with the piston rod (502). Its side wall is provided with a strip groove (7011) that cooperates with the hydraulic pipeline (6) on the outside of the cylinder body (501). And a shielding component that dynamically closes the strip (7011). The protective cover (7) includes: The protective tube (701) slides in fit with the cylinder body (501); The hinge plate (702) is fixed to the end of the protective tube (701) and is connected to the hinge seat (12) at the end of the piston rod (502) by a pin. The strip groove (7011) extends axially along the protective tube (701), and a first opening is provided on the side near the hinge seat (12) connected to the cylinder body (501). The occlusion component includes: Arc-shaped grooves (8) are symmetrically opened on the inner walls of both sides of the strip groove (7011); Multiple arc-shaped baffles (801) are provided and are slidably embedded in the arc-shaped grooves (8) in a row; An elastic element (802) is disposed between the arc-shaped baffle (801) and the arc-shaped groove (8); Among them, the arc-shaped baffles (801) on the same vertical plane in the arc-shaped grooves (8) on both sides move to abut against each other; The protective tube (701) is provided with a guide plate (9) at the outer hydraulic pipeline (6). Each arc-shaped baffle (801) has a force plate (10) at its bottom that moves against the guide plate (9). Both the guide plate (9) and the force plate (10) have matching extrusion slopes.

2. The servo-driven hydraulic grab system for a large crane according to claim 1, characterized in that, The hydraulic pump group (2) includes multiple uniformly distributed constant power high-pressure piston variable pumps. The variable pumps are coaxially connected to the servo motor, and the pump outlets are connected in parallel to the hydraulic pump head valve group (3) through hydraulic pipelines (6).

3. A servo-driven hydraulic grab system for a large crane according to claim 2, characterized in that, The control valve assembly (4) includes: The rodless chamber inlet valve assembly (401) and the rod chamber inlet valve assembly (402) of the hydraulic cylinder. The rodless chamber return valve assembly (404) and the rod chamber return valve assembly (403) of the hydraulic cylinder. A differential valve assembly (405) is connected between the rodless chamber and the rod chamber to form a differential control circuit to drive the piston rod (502) to move by utilizing the area difference between the two ends of the piston; The pressure relief valve assembly (406) is connected in parallel between the rodless chamber oil passage and the oil tank (1); The safety valve (407) is connected in series at the end of the main oil circuit, and its overflow port is directly connected to the oil tank (1).

4. A servo-driven hydraulic grab system for a large crane according to claim 3, characterized in that, In the control valve assembly (4): The rodless chamber inlet valve group (401) and the rod chamber inlet valve group (402) are connected in parallel in the main oil circuit. The inlets of both are connected to the output end of the hydraulic pump head valve group (3), and the outlets are connected to the rodless chamber and the rod chamber of the hydraulic cylinder body (5) through hydraulic pipelines (6), respectively. The solenoid valve of the differential valve group (405) of the control valve group (4) is a three-position four-way valve. Its port A is connected to the inlet of the rodless chamber oil inlet valve group (401), and its port B is connected to the outlet of the rod chamber oil return valve group (403), forming a diagonal connection structure of the differential oil circuit.

5. A servo-driven hydraulic grab system for a large crane according to claim 4, characterized in that, The hydraulic cylinder body (5) also includes: The hinge seat (12) has two ends that are respectively connected to the cylinder body (501) and the piston rod (502). The hinge seat (12) at the end of the piston rod (502) has a recess (121) for connecting with the hydraulic grab bucket.

6. A servo-driven hydraulic grab system for a large crane according to claim 1, characterized in that, The protective tube (701) has a second opening at one end away from the cylinder body (501), and an annular groove (11) is formed at the second opening of the protective tube (701). The annular groove (11) has the following circumferentially distributed features: Support plate assembly, each support plate assembly consists of two support plates (111) arranged in pairs. A rotating shaft (112) is mounted between two support plates (111). A movable plate (113) is connected to the outside of the rotating shaft (112) by a torsion spring and moves against the inner wall of the annular groove (11). A brush (114) fixed to the end of the movable plate (113). The brush (114) maintains elastic contact with the surface of the piston rod (502).

7. A grab bucket, applicable to the servo-driven hydraulic grab bucket system for a large crane as described in claim 6, characterized in that, It includes a bucket base connected to the crane wire rope and two buckets hinged to the bucket base. The buckets are connected to the piston rod (502) of the hydraulic cylinder body (5). The opening and closing of the buckets are driven by the hydraulic cylinder body (5) controlled by the hydraulic control system.

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