Swing cylinder

Abstract

The application relates to the technical field of swing oil cylinders, in particular to a swing oil cylinder which comprises a cylinder body, an end cover, a piston, and is further provided with a first locking nut which is fixedly connected with the cylinder body, and the hydraulic pressure borne by an output shaft body is transmitted to the cylinder body; the end cover is fixedly connected with the cylinder body, and the reaction force of the hydraulic pressure for moving the piston to a first chamber is transmitted to the cylinder body; the two jointly act on the hydraulic pressure for reciprocating the piston, and the hydraulic pressure no longer directly acts on the output shaft body, so that the reaction force of the hydraulic pressure for reciprocating the piston borne by the output shaft body is not transmitted to a thrust washer or a needle bearing, the thrust washer or the needle bearing is prevented from rotating and rubbing under the condition of bearing huge hydraulic pressure, is quickly abraded or damaged, and a shaft jamming fault is caused, and the service life of a thrust part is prolonged.

Description

Technical Field

[0001] This application relates to the field of swing cylinder technology, and more particularly to a swing cylinder. Background Technology

[0002] A oscillating cylinder is a hydraulic actuator capable of reciprocating oscillating motion. Due to its compact structure and high output torque, it plays a vital role in various industrial machinery and engineering equipment. It uses the pressure of hydraulic oil to drive the movement of internal components, converting hydraulic energy into mechanical energy, thereby driving the load to complete a rotational movement at a specific angle. The stability and reliability of its performance directly affect the overall operating efficiency of the equipment. For example... Figure 1 The diagram shows a schematic of an existing swing cylinder structure. The main seal 100 and guide ring 200 are usually set in the outer circular groove of the output shaft 300 and the rear end cover 400. The rear end cover 400 and the output shaft 300 are fixed and rotate synchronously by splines or threaded pins. The thrust washers or needle roller bearings 500 at both ends play the role of axial positioning and bearing axial force.

[0003] In the field of aerial work platforms, the swing cylinder is the core component that drives the platform basket to rotate. During operation, the swing cylinder flexibly adjusts the position of the basket to meet the needs of different work points. At this time, the swing cylinder must not only bear the weight of the platform basket itself, the personnel and tools it carries, but also cope with potential off-center loads during operation. This places extremely high demands on its load-bearing capacity, off-center load resistance, and operational stability.

[0004] In the field of quick-change rotary attachments for excavators, the rotary cylinder is the core component driving the rotation of the bucket or excavator attachments. Due to the frequent occurrence of unforeseen overload situations, the rotary cylinder is subjected to enormous bending moments instantaneously, placing higher demands on its ability to withstand bending moments and resist impacts.

[0005] However, the existing structure of the swing cylinder has significant drawbacks in off-center load applications: First, the output shaft 300 and end cover 400 are locked together, axially positioned by the thrust pad 500, and the piston 600 is limited by the end faces of the output shaft 300 and end cover 400 under hydraulic pressure. When transmitting torque, the output shaft 300 is subjected to huge axial forces and reaction forces generated by the reciprocating motion of the piston 600. This axial force, combined with the external off-center bending moment, causes the thrust pad or needle roller bearing 500 to rotate and rub under a combined load of tens of tons, leading to its rapid deterioration. Firstly, rapid wear or breakage; secondly, uneven load causes unilateral wear of the guide ring 200, which in turn causes eccentric movement of the output shaft 300, increasing the dynamic clearance at the main seal 100. High-pressure oil can easily squeeze the sealing lip into the gap, causing shear damage and leakage failure. In addition, the traditional structure places the seal on the output shaft 300. To avoid iron-grinding failure between the output shaft 300 and the cylinder 700, a larger seal extrusion gap (usually above 0.2mm) is designed, which further exacerbates the risk of seal extrusion. This results in a high failure rate and short service life of the traditional swing cylinder under uneven load conditions. Summary of the Invention

[0006] To solve the above problems, this application provides a swing cylinder, comprising:

[0007] A cylinder body, wherein a channel extending along its axial direction is provided inside the cylinder body;

[0008] An output shaft body, at least a portion of which extends into the channel of the cylinder body, forming a piston channel with the cylinder body;

[0009] An end cap, located at one end of the cylinder body, is used to close the end of the piston passage;

[0010] A piston is located within the piston channel. The outer wall of the piston is provided with external helical teeth, which mesh with the internal helical teeth on the inner wall of the cylinder to form a helical transmission pair. The piston divides the piston channel into a first chamber and a second chamber. The cylinder is provided with a first oil supply hole communicating with the first chamber and a second oil supply hole communicating with the second chamber.

[0011] A first locking nut is also provided, and the first locking nut and the end cap are fixedly mounted on the inner wall of the cylinder.

[0012] In one embodiment, the inner wall of the piston is provided with internal splines, and the output shaft body and the internal splines of the piston form a spline meshing transmission pair, wherein the spline meshing transmission pair is a helical gear transmission or a spur gear transmission.

[0013] In one embodiment, the spline meshing transmission pair is a spur spline meshing transmission pair.

[0014] In one embodiment, the output shaft body includes an output shaft and an inner shaft. The inner shaft is provided with an external spur spline that meshes with an internal spur spline on the inner wall of the piston to form a first spur spline meshing transmission pair. The inner shaft is provided with an internal spur spline, and the output shaft is provided with an external spur spline. The external spur spline on the output shaft meshes with the internal spur spline on the inner shaft to form a second spur spline meshing transmission pair. The output shaft is provided with an output shaft positioning step, and the inner shaft is provided with an inner shaft positioning step. The output shaft and the inner shaft are in a stop-and-hold engagement.

[0015] In one embodiment, a locking and positioning step is provided on the inner shaft, and the first locking nut is located at the locking and positioning step. The first locking nut is located between the inner shaft and the output shaft, and the first locking nut is made of wear-resistant ductile iron and lubricated with anti-wear grease.

[0016] In one embodiment, a second locking nut is also provided. The second locking nut is disposed on the output shaft body and located near the end cover. The second locking nut is connected to the shaft head locking thread on the output shaft, and after tightening, it is fixed with a threaded pin and rotates synchronously with the output shaft.

[0017] In one embodiment, a first axial load element is sleeved on the inner shaft. The first axial load element is a thrust washer or a needle roller bearing. The first axial load element is located between the bearing positioning step of the inner shaft and the positioning step of the cylinder. The bearing positioning step is an annular shoulder that provides axial limitation for the first axial load element. The first locking nut is located outside the first axial load element, which locks and positions the first axial load element and allows for adjustment of its clearance.

[0018] In one embodiment, the end cap is provided with an external thread that engages with the internal thread of the cylinder body to fix the end cap on the cylinder body. The end cap is provided with a bearing mounting position, and a second axial load element is provided in the bearing mounting position. The second axial load element is a thrust washer or a needle roller bearing. The second axial load element is located between the end cap and the second locking nut. One side of the second axial load element contacts the end face of the bearing mounting position of the end cap, and the other side contacts the end face of the second locking nut.

[0019] In one embodiment, a first guide ring is provided at the power output end of the output shaft. The outer ring of the first guide ring mates with the inner wall of the cylinder body, and the inner ring of the first guide ring mates with the outer wall of the output shaft, and they are radially distributed between the output shaft and the cylinder body. A guide ring mounting position is provided on the end cover, and a second guide ring is provided in the guide ring mounting position. The outer ring of the second guide ring mates with the inner wall of the end cover, and the inner ring of the second guide ring mates with the outer wall of the second locking nut, and they are radially distributed between the second locking nut and the end cover. Both the first guide ring and the second guide ring are made of iron-based oil-free lubricated bushings.

[0020] In one embodiment, a plurality of sealing components are also provided. A first main seal is provided between the inner shaft and the cylinder body, installed in the sealing groove of the cylinder body and in close contact with the outer wall of the inner shaft. A static seal for the shaft is provided between the output shaft and the inner shaft, installed in the sealing groove of the inner shaft. A second main seal is provided between the end cover and the cylinder body, installed in the sealing groove of the end cover. A rotary dynamic seal for the shaft is provided between the end cover and the output shaft, installed in the sealing groove of the end cover and in close contact with the outer wall of the output shaft.

[0021] In one embodiment, the second spur spline meshing transmission pair has a small module and a high number of teeth structure, and the rotation starting point of the output shaft can be adjusted by changing the position of the meshing teeth between the output shaft and the inner shaft.

[0022] In one embodiment, the internal helical teeth on the inner wall of the cylinder can be integrally formed with the cylinder body, or they can be fixedly installed on the inner wall of the cylinder body channel using a separately machined internal tooth fixing component. A first piston seal for sealing hydraulic oil is provided between the piston and the cylinder body, and a second piston seal for sealing hydraulic oil is provided between the piston and the output shaft body. The first piston seal and the second piston seal can be located on the same side of the piston or on opposite sides of the piston.

[0023] In one embodiment, the output shaft can be designed as an integral output shaft or as a split output shaft; the split output shaft is broken off from the side away from the power output end of the output shaft from the second spur spline engagement point, and is divided into a sealing section that extends into the piston channel and an output section for power output; the sealing section cooperates with the piston to achieve sealing; the output section of the output shaft can be a flange with a threaded hole or an adapter to adapt to various regular and irregular geometric connection methods, such as one or more of spline output, flat key output, and square key output connection methods.

[0024] The beneficial effects of this application are as follows:

[0025] This application provides a swing cylinder. A first locking nut is fixedly connected to the cylinder body. When the piston moves towards the second chamber, the hydraulic pressure borne by the output shaft body is transmitted to the cylinder body through the first locking nut. An end cover is fixedly connected to the cylinder body. When the piston moves towards the first chamber, the hydraulic pressure borne by the output shaft body is transmitted to the cylinder body through the end cover. The combined effect of these two components prevents the hydraulic pressure driving the piston reciprocating from directly acting on the output shaft body. This avoids the output shaft body transmitting the reaction force of the hydraulic pressure driving the piston reciprocating to the thrust washer or needle roller bearing, thus reducing the thrust... Under immense hydraulic pressure, the gaskets or needle roller bearings experience rapid wear or failure due to rotational friction, leading to shaft failure and extending the service life of the thrust components. The first locking nut and the output shaft body end face are engaged with the cylinder positioning step via the first shaft load element. Combined with the external guide ring, these two elements significantly improve the overall structure's resistance to eccentric bending moments, preventing seal failure due to increased extrusion gap caused by eccentric loading. This further enhances the sealing reliability of the swing cylinder, reduces oil leakage, and ensures long-term stable operation. The swing cylinder of this application is particularly suitable for aerial work platforms and excavator attachment rotation applications. Its core advantage lies in the dual optimization of structural and stress design. The first locking nut is fixedly connected to the cylinder body, and the end cover is also fixedly connected to the cylinder body. Together, they transmit the hydraulic pressure and reaction force driving the piston's reciprocating motion to the cylinder body, preventing axial force impact on the thrust components. Furthermore, the external guide ring further enhances the overall structure's resistance to eccentric bending moments, ensuring stable operation of the cylinder under eccentric loading conditions. Based on this, the spur spline meshing transmission pair formed by the spur spline inside the piston wall and the output shaft body only transmits torque without axial force, so that the output shaft body only bears the static load of the platform. The spur design eliminates axial force. When filled with oil or under off-center load, the shaft load element is only subjected to the static load of the platform and there is no hydraulic impact force, which greatly reduces the risk of wear, ensures stable operation, extends service life, and meets the high requirements of equipment reliability in this field.

[0026] The split design of the inner shaft and output shaft, through a two-stage spur spline pair series transmission combined with end face stop positioning, achieves functional separation and anti-interference optimization. The precision sealing fit between the inner shaft and the cylinder block allows for individual dimensional optimization for high-pressure sealing, effectively isolating the external off-center load and bending moment on the output shaft from interference with the sealing system. The slight clearance (e.g., 0.1mm) in the spline meshing provides adaptive buffer space when the output shaft is subjected to external force eccentricity, preventing damage to the inner shaft and cylinder block seals due to rigid interference. At the same time, the output shaft can be flexibly disassembled or replaced as an independent module. The output shaft can be a flange with threaded holes or an adapter, adapting to various regular and irregular geometric connection methods, such as one or more of spline output, flat key output, and square key output, greatly improving the product's adaptability to operating conditions, ease of maintenance, and functional expandability. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the existing technology structure;

[0028] Figure 2 This is a schematic diagram of the structure of this application;

[0029] Figure 3 This is a schematic diagram of the split structure of the output shaft main body of this application;

[0030] Figure 4 This is a schematic diagram of the split structure of the output shaft in this application;

[0031] Figure 5 A schematic diagram showing the piston seals located on both sides of the piston.

[0032] Explanation of symbols in the diagram:

[0033] 100. Main seal; 200. Guide ring; 300. Output shaft; 400. Rear end cover; 500. Thrust washer or needle roller bearing; 600. Piston; 700. Cylinder block;

[0034] 1. Cylinder block; 11. First oil inlet; 12. Second oil inlet;

[0035] 2. Output shaft body;

[0036] 21. Output shaft;

[0037] 22. Inner shaft; 221. Locking and positioning step; 222. Bearing positioning step;

[0038] 23. First locking nut; 24. Second locking nut; 25. First shaft load element; 26. Second shaft load element; 27. First guide ring; 28. Second guide ring;

[0039] 3. Piston passage; 31. First chamber; 32. Second chamber;

[0040] 4. End caps;

[0041] 5. Piston;

[0042] 6. Screw drive pair;

[0043] 7. Spline meshing transmission pair; 71. First spur spline meshing transmission pair; 72. Second spur spline meshing transmission pair;

[0044] 81. First main seal; 82. Static seal for shaft; 83. Second main seal; 84. Rotary seal for shaft. Detailed Implementation

[0045] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0046] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0047] like Figure 2 , 3 As shown, a swing cylinder includes:

[0048] Cylinder body 1, wherein a channel extending axially is provided inside the cylinder body 1;

[0049] The output shaft body 2 has at least a portion extending into the channel of the cylinder body 1, forming a piston channel 3 between it and the cylinder body 1.

[0050] End cap 4, located at one end of the cylinder body 1, is used to close the end of the piston channel 3;

[0051] Piston 5 is located inside piston channel 3. The outer wall of piston 5 is provided with external helical teeth, which mesh with the internal helical teeth on the inner wall of cylinder 1 to form a helical transmission pair 6. Piston 5 divides piston channel 3 into a first chamber 31 and a second chamber 32. Cylinder 1 is provided with a first oil supply hole 11 communicating with the first chamber 31 and a second oil supply hole 12 communicating with the second chamber 32.

[0052] A first locking nut 23 is also provided, which is fixedly installed on the inner wall of the cylinder body 1.

[0053] Specifically, the cylinder body 1 has an axially extending channel inside, providing installation space for other components. At least a portion of the output shaft body 2 extends into the channel of the cylinder body 1, and an annular piston channel 3 is formed between the outer wall of the output shaft body 2 and the inner wall of the cylinder body 1. The end cap 4 is located at one end of the cylinder body 1, forming a seal at the end of the piston channel 3. The piston 5 is assembled in the piston channel 3, and the outer helical teeth of the outer wall of the piston 5 mesh with the inner helical teeth of the inner wall of the cylinder body 1 to form a helical transmission pair 6. At the same time, the piston 5 divides the piston channel 3 into an independent first chamber 31 and a second chamber 32. The cylinder body 1 also has a first oil supply hole 11 and a second oil supply hole 12 that communicate with the first chamber 31 and the second chamber 32, respectively. The first locking nut 23 is located inside the cylinder body 1 and is fixedly installed on the inner wall of the cylinder body 1, located at the power output end of the output shaft body 2. When hydraulic oil enters the first chamber 31 through the first oil inlet 11, the hydraulic thrust pushes the piston 5 to move toward the second chamber 32. Because the piston 5 meshes with the helical teeth of the cylinder 1, the piston 5 generates rotational motion while moving axially, thereby driving the output shaft body 2 to rotate synchronously. When hydraulic oil enters the second chamber 32 through the second oil inlet 12, the piston 5 moves axially in the opposite direction and rotates in the opposite direction. Through the same transmission path, it drives the output shaft body 2 to rotate in the opposite direction, ultimately realizing the clockwise-counterclockwise cyclic swing of the output shaft body 2. In this application, the first locking nut 23 is fixedly connected to the cylinder body 1. When the piston 5 moves towards the second chamber 32, the hydraulic pressure borne by the output shaft body 2 is transmitted to the cylinder body 1 through the first locking nut 23. This prevents the hydraulic pressure that drives the piston 5 from directly acting on the output shaft body 2, thus avoiding the output shaft body 2 transmitting the reaction force of the hydraulic pressure that drives the piston 5 to the thrust pad or needle roller bearing. This would prevent the thrust pad or needle roller bearing from rotating and rubbing under huge hydraulic pressure, causing it to wear or break quickly, resulting in shaft failure and extending the service life of the thrust component.

[0054] like Figure 2 As shown, the inner wall of the piston 5 is provided with internal splines, and the output shaft body 2 and the internal splines of the piston 5 form a spline meshing transmission pair 7. The spline meshing transmission pair 7 is a helical gear transmission or a spur gear transmission.

[0055] Specifically, the inner wall of the piston 5 is provided with internal tooth splines, which form a spline meshing transmission pair 7 with the output shaft body 2. The spline meshing transmission pair 7 can be a helical tooth transmission or a spur tooth transmission, which can be flexibly selected according to actual needs to take into account the performance requirements of different scenarios.

[0056] like Figure 2 As shown, the spline meshing transmission pair 7 is a spur spline meshing transmission pair.

[0057] Specifically, the spline meshing transmission pair 7 is a spur spline meshing transmission pair. Utilizing the characteristic of spur spline transmission that it only transmits torque and does not generate axial force, the output shaft body 2 only bears torque when receiving the rotational motion transmitted by the piston 5, completely avoiding the generation of axial force. According to the principle of action and reaction force, the impact of axial force in the traditional structure is completely eliminated. This solves the problems of axial force acting on the thrust component due to the use of helical gear meshing between the piston and the output shaft in traditional hydraulic cylinders, which leads to wear of thrust shims or needle roller bearings, output shaft misalignment, hydraulic cylinder jamming, or even failure. This significantly extends the service life and operational stability of the swing hydraulic cylinder.

[0058] like Figure 2 , 3 As shown, the output shaft body 2 includes an output shaft 21 and an inner shaft 22. The inner shaft 22 is provided with an external spur spline, which meshes with the internal spur spline on the inner wall of the piston 5 to form a first spur spline meshing transmission pair 71. The inner shaft 22 is provided with an internal spur spline, and the output shaft 21 is provided with an external spur spline. The external spur spline on the output shaft 21 meshes with the internal spur spline on the inner shaft 22 to form a second spur spline meshing transmission pair 72. The output shaft 21 is provided with an output shaft positioning step, and the inner shaft 22 is provided with an inner shaft positioning step. The output shaft 21 and the inner shaft 22 are in a stop-and-hold fit.

[0059] Specifically, the split design of the inner shaft 22 and the output shaft 21, through a two-stage spur spline pair series transmission combined with end face stop positioning, achieves functional separation and anti-interference optimization. The precision sealing fit between the inner shaft 22 and the cylinder 1 allows for separate dimensional optimization for high-pressure sealing, effectively isolating the external off-center load and bending moment on the output shaft 21 from interference with the sealing system. The slight clearance (e.g., 0.1mm) in the spline meshing provides an adaptive buffer space for the output shaft 21 when subjected to external force eccentricity, preventing damage to the seals of the inner shaft 22 and the cylinder 1 due to rigid interference. At the same time, the output shaft 21 can be flexibly disassembled or replaced as an independent module. The output shaft 21 can be a flange with a threaded hole or an adapter, adapting to various regular and irregular geometric connection methods, such as one or more of spline output, flat key output, and square key output, greatly improving the product's adaptability to operating conditions, ease of maintenance, and functional expandability.

[0060] like Figure 3 As shown, a locking and positioning step 221 is provided on the inner shaft 22, and the first locking nut 23 is located at the locking and positioning step 221. The first locking nut 23 is located between the inner shaft 22 and the output shaft 21. The first locking nut 23 is made of wear-resistant ductile iron and is lubricated with anti-wear grease.

[0061] Specifically, the first locking nut 23 is located at the locking positioning step 221 of the inner shaft 22 and between the inner shaft 22 and the output shaft 21. The locking positioning step 221 provides an installation positioning reference and transmits the hydraulic pressure borne by the inner shaft 22 and the output shaft 21 to the cylinder 1. The wear-resistant ductile iron material and anti-wear grease lubrication can improve the pressure resistance and wear resistance and reduce friction loss.

[0062] like Figure 2 , 3 As shown, a second locking nut 24 is also provided. The second locking nut 24 is provided on the output shaft body 2. The second locking nut 24 is located on the side close to the end cover 4. The second locking nut 24 is connected to the shaft head locking thread on the output shaft 21. After tightening, it is fixed with a threaded pin and rotates synchronously with the output shaft 21.

[0063] Specifically, the second locking nut 24 is connected to the shaft head by a locking thread. After tightening, it is fixed with a threaded pin and rotates synchronously with the output shaft 21. Through its cooperation with the end cover 4, it transmits the hydraulic pressure borne by the output shaft body 2 to the cylinder body 1, avoiding the hydraulic pressure from acting directly on the output shaft body 2. The double positioning structure formed by the first locking nut 23 and the second locking nut 24 reduces the eccentricity of the output shaft body 2 through positioning, preventing the seal from being crushed due to eccentricity, further improving the sealing reliability of the swing cylinder, reducing oil leakage failures, and ensuring the long-term stable operation of the swing cylinder.

[0064] like Figure 3 As shown, a first shaft load element 25 is sleeved on the inner shaft 22. The first shaft load element 25 is a thrust washer or a needle roller bearing. The first shaft load element 25 is located between the bearing positioning step 222 of the inner shaft 22 and the positioning step of the cylinder 1. The bearing positioning step 222 of the inner shaft 22 is an annular shoulder, which forms an axial limit on the first shaft load element 25. The first locking nut 23 is located outside the first shaft load element 25, which forms a locking position on the first shaft load element 25 and can adjust its clearance.

[0065] Specifically, the annular shoulder of the inner shaft 22 and the positioning step of the cylinder body 1 together form an axial limit for the first shaft load element 25, ensuring that the first shaft load element 25 is stable in position when under force and avoiding axial movement; the first shaft load element 25 significantly reduces the friction force when the inner shaft 22 rotates through rolling friction characteristics; the first locking nut 23 can not only reliably lock and position the bearing, but also flexibly adjust its clearance, ensuring that the first shaft load element 25 is always in the best working state; the overall structure transmits external force to the cylinder body 1 through the first shaft load element 25 and the first locking nut 23, avoiding direct deformation of the inner shaft 22 under force, while improving the smoothness of transmission and the service life of components.

[0066] like Figure 3 As shown, the end cover 4 is provided with an external thread that engages with the internal thread of the cylinder body 1, thereby fixing the end cover 4 onto the cylinder body 1. The end cover 4 is provided with a bearing mounting position, and a second shaft load element 26 is provided in the bearing mounting position. The second shaft load element 26 is a thrust washer or a needle roller bearing. The second shaft load element 26 is located between the end cover 4 and the second locking nut 24. One end of the second shaft load element 26 contacts the end face of the bearing mounting position of the end cover 4, and the other end contacts the end face of the second locking nut 24.

[0067] Specifically, the end cover 4 is securely connected to the cylinder body 1 via an external thread. A second shaft load element 26, positioned in its bearing mounting location, is located between the end cover 4 and the second locking nut 24, with both ends contacting the bearing mounting face of the end cover 4 and the end face of the second locking nut 24, respectively. The end cover 4 is fixedly mounted on the cylinder body 1, ensuring not only the sealing of the assembly between the end cover 4 and the cylinder body 1 to prevent hydraulic oil leakage, but also ensuring the stability of the mounting position of the second shaft load element 26. The second shaft load element 26 reduces the frictional resistance of the output shaft 21 during rotation through rolling friction. The end cover 4 is fixedly connected to the cylinder body 1. When the piston 5 moves towards the first chamber 31, the hydraulic pressure borne by the output shaft body 2 is transmitted to the cylinder body 1 through the end cover 4. This prevents the hydraulic pressure driving the piston 5 from directly acting on the output shaft body 2, thus avoiding the output shaft body 2 transmitting the reaction force of the hydraulic pressure driving the piston 5 to the thrust washer or needle roller bearing.

[0068] like Figure 3 As shown, the power output end of the output shaft 21 is provided with a first guide ring 27. The outer ring of the first guide ring 27 mates with the inner wall of the cylinder 1, and the inner ring of the first guide ring 27 mates with the outer wall of the output shaft 21. They are radially distributed between the output shaft 21 and the cylinder 1. The end cover 4 is provided with a guide ring mounting position. A second guide ring 28 is provided in the guide ring mounting position. The outer ring of the second guide ring 28 mates with the inner wall of the end cover 4, and the inner ring of the second guide ring 28 mates with the outer wall of the second locking nut 24. They are radially distributed between the second locking nut 24 and the end cover 4. Both the first guide ring 27 and the second guide ring 28 are made of iron-based oil-free lubricated bushings.

[0069] Specifically, the first guide ring 27 is radially distributed between the output shaft 21 and the cylinder body 1, with the outer ring fitting with the inner wall of the cylinder body 1 and the inner ring fitting with the outer wall of the output shaft 21. The second guide ring 28 is located in the guide ring mounting position of the end cover 4, with the outer ring fitting with the inner wall of the end cover 4 and the inner ring fitting with the outer wall of the second locking nut 24. Its installation structure eliminates the limitation of traditional hydraulic cylinder guide rings requiring internal grooves for installation, thus increasing the bearing area of ​​the guide ring. At the same time, both use high-load-bearing iron-based oilless lubricated bushings, further increasing the overall bearing capacity and effectively solving the problems of traditional guide rings having low pressure-bearing capacity due to limited area, rapid wear under off-center load, easy eccentricity of the output shaft 21, increased seal extrusion gap, seal damage, and hydraulic cylinder oil leakage failure. In addition, the external design of the guide ring avoids the disadvantage of contaminating the entire hydraulic system after the wear of the traditional internal guide ring, and can also provide stable radial support for the output shaft 21 and the second locking nut 24, reducing friction during movement.

[0070] like Figure 3 As shown, multiple sealing components are also provided. A first main seal 81 is provided between the inner shaft 22 and the cylinder body 1, installed in the sealing groove of the cylinder body 1, and in close contact with the outer wall of the inner shaft 22. A static seal 82 for the shaft is provided between the output shaft 21 and the inner shaft 22, installed in the sealing groove of the inner shaft 22. A second main seal 83 is provided between the end cover 4 and the cylinder body 1, installed in the sealing groove of the end cover 4. A rotary seal 84 for the shaft is provided between the end cover 4 and the output shaft 21, installed in the sealing groove of the end cover 4, and in close contact with the outer wall of the output shaft 21.

[0071] Specifically, the first main seal 81 is a rotary dynamic seal, installed in the groove of the cylinder body 1. Due to the separate design of the inner shaft 22 and the output shaft 21, the inner shaft 22 can focus on the sealing function, and the dimensional accuracy of its mating surface can be independently optimized, which significantly reduces the extrusion gap of the first main seal 81 (far lower than the 0.2-0.3mm of the traditional design). The extremely small design gap avoids shear damage caused by high-pressure oil squeezing the sealing lip into the gap, greatly improving the service life and reliability of the first main seal 81 under high pressure and off-center load conditions, and solving the pain point of easy extrusion failure of traditional cylinder main seals. A shaft static seal 82 is provided between the output shaft 21 and the inner shaft 22. The output shaft 21 and the inner shaft 22 are connected by end face stop fit. Since the two are connected by splines and rotate synchronously without relative movement, friction and wear are avoided, and the service life of the seal is improved. The end cover 4 is fixedly installed on the cylinder body 1 and does not rotate with the output shaft 21, so that a static seal is formed between the end cover 4 and the cylinder body 1, which significantly extends the service life of the seal in this part. A shaft rotary dynamic seal 84 is provided between the end cover 4 and the output shaft 21. Since the output shaft 21 is fixedly connected to the second locking nut 24 and positioned by a threaded pin, and a second guide ring 28 is radially provided between the second locking nut 24 and the end cover 4, the coaxiality of the output shaft 21 and the end cover 4 can be effectively guaranteed. Therefore, the extrusion gap of the shaft rotary dynamic seal 84 can be appropriately reduced, thereby greatly improving the service life of the dynamic seal.

[0072] like Figure 3 As shown, the second spur spline meshing transmission pair 72 has a small module and a high number of teeth structure. The starting point of rotation of the output shaft 21 can be adjusted by changing the meshing teeth position of the output shaft 21 and the inner shaft 22.

[0073] Specifically, the module is numerically equal to the ratio of the pitch circle diameter (d) to the number of teeth (z) (m=d / z). The smaller the module, the more teeth can be arranged for the same diameter. The spur spline meshing transmission pair adopts a small module and multiple tooth structure, which can achieve more precise indexing for the same diameter. The angular deviation can be controlled within 4 degrees, meeting the product's error standard of ±2 degrees for a 180-degree rotation angle. This effectively avoids the problem of excessive angular deviation caused by misaligned teeth in large module gears, significantly improving indexing accuracy. By changing the position of the meshing teeth to adjust the starting point of the output shaft 21 rotation, the assembly flexibility and efficiency are greatly improved, balancing accuracy and assembly convenience.

[0074] like Figure 3 , 5As shown, the inner helical teeth on the inner wall of the cylinder body 1 can be integrally formed with the cylinder body 1, or they can be fixedly installed on the inner wall of the channel of the cylinder body 1 by a separately machined inner tooth fixing part. A first piston seal for sealing hydraulic oil is provided between the piston 5 and the cylinder body 1, and a second piston seal for sealing hydraulic oil is provided between the piston 5 and the output shaft body 2. The first piston seal and the second piston seal can be located on the same side of the piston 5 or they can be located on opposite sides of the piston 5.

[0075] Specifically, the one-piece molding structure ensures the integrity of the internal helical teeth and the cylinder body 1, guaranteeing structural strength. When using separately machined internal tooth fixing parts, if it is necessary to adapt to pistons 5 with different parameters, only the internal tooth fixing parts need to be replaced, which can flexibly meet the requirements of different working conditions for helical tooth parameters. The first piston seal and the second piston seal can be located on the same side of the piston 5 or on opposite sides. The two layout methods can be flexibly selected according to the overall structural dimensions of the swing cylinder, the internal chamber space, and the assembly process requirements.

[0076] like Figure 3 , 4 As shown, the output shaft 21 can be designed as an integral output shaft or as a split output shaft; the split output shaft is disconnected from the power output end of the output shaft 21 at the second spur spline meshing transmission pair 72, and is divided into a sealing section that extends into the piston channel 3 and an output section for power output; the sealing section cooperates with the piston 5 to achieve sealing; the output section of the output shaft 21 can be a flange with a threaded hole or an adapter to adapt to various regular and irregular geometric connection methods, such as one or more of spline output, flat key output, and square key output connection methods.

[0077] Specifically, the integrated design ensures the overall rigidity and transmission stability of the output shaft 21, making it suitable for scenarios with high structural strength requirements; such as Figure 4 As shown, in the split design of the output shaft 21, the sealing section only cooperates with the piston 5 to achieve sealing without bearing external forces and bending moments, which can reduce the impact of external forces on sealing performance and extend the life of the seals. The output section can focus on power output. The clear division of labor between the two improves the structural reliability. At the same time, the output section of the output shaft 21 can be a flange with a threaded hole or an adapter to adapt to various regular and irregular geometric connection methods, such as spline output, flat key output, square key output, etc. It can flexibly adapt to the installation requirements of different equipment, meet diverse working conditions without modifying the core components inside the cylinder, reduce equipment adaptation costs, and enhance the versatility of the product.

[0078] This application discloses a swing cylinder in which, when hydraulic oil enters the second chamber 32 through the second oil inlet 12, the piston 5 moves axially in the opposite direction and rotates in the opposite direction. Through the same transmission path, it drives the output shaft body 2 to rotate in the opposite direction, ultimately realizing the clockwise-counterclockwise cyclic swing of the output shaft body 2. In this application, the first locking nut 23 is fixedly connected to the cylinder body 1. When the piston 5 moves towards the second chamber 32, the hydraulic pressure borne by the output shaft body 2 is transmitted to the cylinder body 1 through the first locking nut 23. The end cover 4 is fixedly connected to the cylinder body 1. When the piston 5 moves towards the first chamber 31, the hydraulic pressure borne by the output shaft body 2 is transmitted to the cylinder body 1 through the end cover 4. The two work together to prevent the hydraulic pressure that drives the piston 5 to reciprocate from directly acting on the output shaft body 2. This avoids the output shaft body 2 transmitting the reaction force of the hydraulic pressure that drives the piston 5 to reciprocate to the thrust pad or needle roller bearing, which would cause the thrust pad or needle roller bearing to rotate and rub under huge hydraulic pressure, quickly wear or break down, causing shaft failure and extending the service life of the thrust component. The first locking nut 23 and the end face of the output shaft body 2 are engaged with the positioning step of the cylinder body 1 through the first shaft load element 25. Combined with the external arrangement of the guide ring, the two work together to greatly improve the overall structure's resistance to eccentric bending moments, preventing the seals from failing due to increased extrusion gap caused by eccentric loading. This further enhances the sealing reliability of the swing cylinder, reduces oil leakage, and ensures long-term stable operation of the swing cylinder. The swing cylinder of this application is particularly suitable for aerial work platforms and excavator attachment rotation applications. Its core advantage lies in the dual optimization of structural and force design. The first locking nut 23 is fixedly connected to the cylinder body 1, and the end cover 4 is also fixedly connected to the cylinder body 1. Together, they transmit the hydraulic pressure and reaction force that drives the piston 5 to reciprocate to the cylinder body 1, preventing axial force from impacting the thrust component. Furthermore, the external arrangement of the guide ring further enhances the overall structure's resistance to eccentric bending moments, ensuring stable operation of the cylinder under eccentric loading conditions. Based on this, the spur spline meshing transmission pair formed by the inner wall of piston 5 and the output shaft body 2 transmits only torque without axial force, so that the output shaft body 2 only bears the static load of the platform. The spur design eliminates axial force. When filled with oil or under off-center load, the shaft load element is only subjected to the static load of the platform and there is no hydraulic impact force, which greatly reduces the risk of wear, ensures stable operation, extends service life, and meets the high requirements of equipment reliability in this field.

[0079] Taking the swing cylinder of this application as an example, with a working pressure of 21 MPa, a starting pressure of 3.5 MPa, and an output torque of 1600 N·m, when the high-pressure oil input through the first oil inlet 11 is P1 = 21 MPa, the pressure through the second oil inlet 12 is P2 = 3.5 MPa, and the piston's force-bearing area is 7398 mm², the calculated axial work force of the piston is 129475 N. That is to say, to achieve an output torque of 1600 N·m, the force acting on the piston 5 needs to reach 129475 N (approximately 12.9 × 10³ kgf) to drive the piston axially. According to the structural design of this invention, based on the principle of action and reaction, this force will eventually act on the first locking nut 23; conversely, when the second oil inlet 12 is filled with 21MPa high-pressure oil, this force will eventually act on the end cap 4, unlike a traditional swing cylinder, where the force will act on the thrust pad or needle roller bearing, causing the thrust pad or needle roller bearing to rotate while bearing huge pressure, resulting in wear or breakage failure.

[0080] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

[0081] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

Claims

1. A swing cylinder, comprising: A cylinder body (1) is provided with a channel extending along its axial direction; Output shaft body (2), at least a portion of which extends into the channel of the cylinder (1) to form a piston channel (3) with the cylinder (1). End cap (4), the end cap (4) is located at one end of the cylinder (1) and is used to close the end of the piston channel (3); The piston (5) is located in the piston channel (3). The outer wall of the piston (5) is provided with external helical teeth, which mesh with the internal helical teeth on the inner wall of the cylinder to form a helical transmission pair (6). The piston (5) divides the piston channel (3) into a first chamber (31) and a second chamber (32). The cylinder (1) is provided with a first oil supply hole (11) communicating with the first chamber (31) and a second oil supply hole (12) communicating with the second chamber (32). Its features are: A first locking nut (23) is also provided, and the first locking nut (23) and the end cap (4) are fixedly installed on the inner wall of the cylinder body (1).

2. The swing cylinder according to claim 1, characterized in that, The piston (5) has internal spline teeth on its inner wall. The output shaft body (2) and the internal spline teeth of the piston (5) form a spline meshing transmission pair (7). The spline meshing transmission pair (7) is a helical gear transmission or a spur gear transmission.

3. A swing cylinder according to claim 2, characterized in that, The spline meshing transmission pair (7) is a spur spline meshing transmission pair.

4. A swing cylinder according to claim 3, characterized in that, The output shaft body (2) includes an output shaft (21) and an inner shaft (22). The inner shaft (22) is provided with an external spur spline, which meshes with the internal spur spline on the inner wall of the piston (5) to form a first spur spline meshing transmission pair (71). The inner shaft (22) is provided with an internal spur spline, and the output shaft (21) is provided with an external spur spline. The external spur spline on the output shaft (21) meshes with the internal spur spline on the inner shaft (22) to form a second spur spline meshing transmission pair (72). The output shaft (21) is provided with an output shaft positioning step, and the inner shaft (22) is provided with an inner shaft positioning step. The output shaft (21) and the inner shaft (22) are in a stop-and-go fit.

5. A swing cylinder according to claim 4, characterized in that, The inner shaft (22) is provided with a locking and positioning step (221), the first locking nut (23) is located at the locking and positioning step (221), the first locking nut (23) is located between the inner shaft (22) and the output shaft (21), the first locking nut (23) is made of wear-resistant ductile iron material and is lubricated with anti-wear grease.

6. A swing cylinder according to claim 5, characterized in that, A second locking nut (24) is also provided. The second locking nut (24) is located on the output shaft body (2). The second locking nut (24) is located on the side close to the end cover (4). The second locking nut (24) is connected to the shaft head locking thread on the output shaft (21). After tightening, it is fixed with a threaded pin and rotates synchronously with the output shaft (21).

7. A swing cylinder according to claim 4, characterized in that, The inner shaft (22) is fitted with a first shaft load element (25), which is a thrust washer or a needle roller bearing. The first shaft load element (25) is located between the bearing positioning step (222) of the inner shaft (22) and the positioning step of the cylinder (1). The bearing positioning step (222) is an annular shoulder, which forms an axial limit on the first shaft load element (25). The first locking nut (23) is located on the outside of the first shaft load element (25), which forms a locking position on the first shaft load element (25) and can adjust its clearance.

8. A swing cylinder according to claim 6, characterized in that, The end cap (4) is provided with an external thread that engages with the internal thread of the cylinder (1) to fix the end cap (4) on the cylinder (1). The end cap (4) is provided with a bearing mounting position, and a second shaft load element (26) is provided in the bearing mounting position. The second shaft load element (26) is a thrust washer or a needle roller bearing. The second shaft load element (26) is located between the end cap (4) and the second locking nut (24). One side of the second shaft load element (26) contacts the end face of the bearing mounting position of the end cap (4), and the other side contacts the end face of the second locking nut (24).

9. A swing cylinder according to claim 6, characterized in that, The output shaft (21) has a first guide ring (27) at its power output end. The outer ring of the first guide ring (27) is fitted with the inner wall of the cylinder (1), and the inner ring of the first guide ring (27) is fitted with the outer wall of the output shaft (21). The guide rings are radially distributed between the output shaft (21) and the cylinder (1). The end cover (4) has a guide ring mounting position. The guide ring mounting position has a second guide ring (28). The outer ring of the second guide ring (28) is fitted with the inner wall of the end cover (4), and the inner ring of the second guide ring (28) is fitted with the outer wall of the second locking nut (24). The guide rings are radially distributed between the second locking nut (24) and the end cover (4). Both the first guide ring (27) and the second guide ring (28) are made of iron-based oil-free lubricated bushings.

10. A swing cylinder according to claim 4, characterized in that, Multiple sealing components are also provided. A first main seal (81) is provided between the inner shaft (22) and the cylinder (1), which is installed in the sealing groove of the cylinder (1) and is in close contact with the outer wall of the inner shaft (22). A static seal (82) for the shaft is provided between the output shaft (21) and the inner shaft (22), which is installed in the sealing groove of the inner shaft (22). A second main seal (83) is provided between the end cover (4) and the cylinder (1), which is installed in the sealing groove of the end cover (4). A rotary seal (84) for the shaft is provided between the end cover (4) and the output shaft (21), which is installed in the sealing groove of the end cover (4) and is in close contact with the outer wall of the output shaft (21).

11. A swing cylinder according to claim 4, characterized in that, The second spur spline meshing transmission pair (72) has a small module and a large number of teeth structure. The starting point of rotation of the output shaft (21) can be adjusted by changing the meshing position of the output shaft (21) and the inner shaft (22).

12. A swing cylinder according to claim 1, characterized in that, The inner spiral teeth of the cylinder body (1) are integrally formed with the cylinder body (1), or are fixedly installed on the inner wall of the channel of the cylinder body (1) by a separately machined inner tooth fixing part. A first piston seal for sealing hydraulic oil is provided between the piston (5) and the cylinder body (1), and a second piston seal for sealing hydraulic oil is provided between the piston (5) and the output shaft body (2). The first piston seal and the second piston seal are located on the same side of the piston (5) or on both sides of the piston (5).

13. A swing cylinder according to claim 4, characterized in that, The output shaft (21) is designed as an integral output shaft or as a split output shaft; the split output shaft is disconnected from the side away from the power output end of the output shaft (21) at the second spur spline meshing point, and is divided into a sealing section that extends into the piston channel and an output section for power output; the sealing section cooperates with the piston (5) to achieve sealing; the output section of the output shaft (21) is a flange or adapter with a threaded hole, which is suitable for various regular and irregular geometric connection methods, such as one or more of spline output, flat key output, and square key output.

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