Built-in anti-torsion type spring reset straight stroke pneumatic actuator

Abstract

A built-in anti-torsion type spring reset straight stroke pneumatic actuator comprises a connecting base, a cylinder barrel and a cylinder cover are arranged on the connecting base, a mounting cavity is formed in the cylinder barrel, a piston assembly is mounted in the mounting cavity, the piston assembly comprises a spring combination with one end fixedly connected with the connecting base, and the other end of the spring combination is connected with a piston. An output connecting shaft penetrating through the connecting base and the piston is arranged in the cylinder barrel, an anti-rotating shaft is further arranged in the mounting cavity, one end of the anti-rotating shaft penetrates through the piston to be fixed to the cylinder cover, and the other end of the anti-rotating shaft is fixed into the connecting base.

Description

Technical Field

[0001] The utility model relates to a straight-stroke pneumatic actuator with a built-in anti-torsion spring return, belonging to the field of valve actuators. Background Art

[0002] Various chemical plants and oil tank farms require a large number of pneumatic gate valves, pneumatic globe valves, and other automatic control valves for on / off applications. These valves must be controlled by pneumatic linear actuators. Furthermore, to ensure that the valves automatically return to the open or closed position in the event of a gas or power failure, spring-return pneumatic actuators are also required.

[0003] During the upward and downward linear operation of the spring-return pneumatic actuator during the valve opening and closing action, since the spring itself has a fixed forward or reverse direction, a certain degree of torsion will always be passively generated when the air source drives the piston up and down. Therefore, some manufacturers use a method of superimposing internal and external double springs, and the molding directions of the two springs are one positive and one reverse. Although this setting solves some of the problems of small-diameter and small-stroke valves, this situation still exists for large-diameter and large-size cylinders, especially gate valves with large strokes. The torsion of the spring during the upward and downward movement not only changes the relative position of the valve disc and the valve seat, affecting the valve sealing performance and the service life of the cylinder, but in serious cases it will also damage the gate, causing the valve to become stuck or completely fail, posing great hidden dangers and potential hazards to on-site equipment.

[0004] To this end, there are now a variety of solutions for improvement, including setting an anti-rotation baffle on the bracket. However, adding an anti-rotation baffle to the bracket will increase the height of the valve by at least one valve stroke, which undoubtedly not only directly and significantly increases the height of the entire valve, but also increases the installation space of the valve and the overall cost of the valve. In addition, the anti-rotation baffle added to the bracket has a rough structure, low anti-rotation effect and accuracy, and cannot fundamentally solve the problem. Utility Model Content

[0005] The purpose of the utility model is to overcome the shortcomings and deficiencies of the prior art and to provide a straight-stroke pneumatic actuator with a built-in anti-torsion spring return.

[0006] A pneumatic actuator with a spring return and internal torsion protection, comprising a connecting base, a cylinder and a cylinder head mounted on the connecting base, a mounting cavity within the cylinder, and a piston assembly mounted within the mounting cavity. The piston assembly comprises a spring assembly fixedly connected to the connecting base at one end and a piston connected at the other end. An output connecting shaft extending through the connecting base and the piston is located within the cylinder. An anti-rotation shaft is also located within the mounting cavity, with one end extending through the piston and fixed to the cylinder head, and the other end fixed to the connecting base. As the piston moves up and down, it moves linearly along the anti-rotation shaft. The piston does not rotate due to spring torsion, completely eliminating torsional torque interference with the piston and ensuring pure linear motion during its vertical stroke. Because the anti-rotation mechanism is internally designed, there is no need for an additional anti-rotation baffle on the bracket. The overall actuator height does not increase with increasing torsion protection requirements, saving vertical mounting space, simplifying the number of components, and reducing manufacturing and assembly costs. The elimination of torsional loads reduces lateral wear on the piston, guide assembly, and seals, reducing fatigue damage to structural components, and significantly extending the cylinder's service life and valve maintenance intervals.

[0007] Preferably, the cylinder head is provided with a first fixing hole, the connecting base is provided with a second fixing hole, and the piston is provided with a through hole, through which the anti-rotation shaft passes and is fixed in the first and second fixing holes. The first and second fixing holes are aligned with the piston through hole, and the anti-rotation shaft is positioned immediately after penetration, eliminating the need for additional positioning parts and simplifying the assembly process. Direct positioning through the main body structure eliminates additional processing and parts, reducing processing costs while maintaining a compact design.

[0008] Furthermore, the number of anti-rotation shafts is at least one. If there are two anti-rotation shafts, they are symmetrically arranged within the piston assembly. The symmetrical arrangement of the two anti-rotation shafts provides a more balanced restraining torque during spring return and compression, further improving the torsional resistance of large-stroke and large-diameter cylinders. While a single-shaft solution can meet general specifications, a symmetrical dual-shaft solution can be used in larger diameter or higher torque environments, providing flexible design options.

[0009] Preferably, the outer periphery of the piston is provided with a first O-ring and a second O-ring for sealing connection with the cylinder. The double rings can be selected with different hardness or materials according to the pressure difference and temperature conditions of the medium, so as to achieve better sealing adaptation for different industrial working conditions (such as high temperature, high pressure, corrosive media).

[0010] Furthermore, a guide ring is provided between the first and second O-rings. This guide ring abuts against the inner wall of the cylinder, preventing the outer periphery of the piston from contacting the inner wall. The guide ring provides lateral guidance, and the piston contacts the cylinder only via the guide ring, reducing friction loss between the O-ring and the cylinder, and lowering actuation energy consumption. The rigid guide ring effectively prevents lateral piston swing, maintains piston concentricity, and further ensures the smoothness of linear motion.

[0011] Preferably, an indicator rod is connected to the output connecting shaft, with the other end of the indicator rod extending out of the cylinder head to indicate the position of the valve or piston switch. The exposed position of the indicator rod allows for quick determination of the current valve or piston opening, avoiding blind operation or misjudgment on site. During installation and commissioning and routine inspections, the stroke position can be observed without removing the flange or blind hole, improving work efficiency.

[0012] Furthermore, the output connecting shaft and indicator rod outer sleeve are respectively fitted with a third O-ring for sealing with the piston and a fourth O-ring for sealing with the cylinder head. The third O-ring ensures airtightness between the output connecting shaft and the piston assembly, preventing leakage of the medium at the shaft hole. The fourth O-ring forms a stable seal where the indicator rod passes through the cylinder head, preventing external dust or liquid from entering the cavity. The double-end sealing design ensures a clean and dry working environment inside the actuator, reducing seal aging or damage caused by contaminants or lubricant leakage. With the output connecting shaft and indicator rod double-end sealed, internal cylinder pressure fluctuations have no external impact, and the indicator structure is also protected from medium corrosion, promoting long-term stable operation.

[0013] Preferably, the spring assembly includes a limiting rod with positioning sleeves at both ends. A spring is sheathed around the positioning sleeves, which compress the spring to a preloaded height. The positioning sleeves precisely control the initial compression of the spring, ensuring that the spring is always in the designed preload state and a consistent and reliable reset force. Once the preload height is fixed, the spring will not produce axial play due to vibration during the reciprocating motion of the piston, thus preventing abnormal noise and loosening. By replacing positioning sleeves of different lengths or diameters, the preload force can be flexibly adjusted without having to replace the entire spring assembly, reducing maintenance costs.

[0014] Preferably, a limit rod is provided on the connecting base. One end of the limit rod extends into the piston assembly, and the other end is adjusted by an adjusting bolt. The upper and lower limit positions of the piston movement can be precisely set by adjusting the bolt, adapting to different stroke requirements without replacing parts. If the valve seal or stroke requirements change, simply loosen the adjusting bolt and reposition the limit rod, completing calibration quickly and reducing downtime. The set height of the limit rod protects the piston and internal components from overtravel impact, extending component life and improving system safety.

[0015] Preferably, the cylinder head is provided with an air inlet passage communicating with the mounting cavity, and the connecting base is provided with an air outlet passage communicating with the piston assembly. The inlet and outlet passages are arranged axially, enabling direct communication between the air source and the piston chamber, resulting in low airflow resistance and high ventilation efficiency. The inlet passage leads directly to the mounting cavity, while the outlet passage reaches directly to the piston lower chamber, shortening the gas inlet and outlet paths and enabling faster and more sensitive opening and closing of the actuator.

[0016] The beneficial effects of the present invention are as follows: When the piston moves up and down, it will move linearly along the anti-rotation shaft. The piston will not rotate due to the torsion of the spring, completely eliminating the interference of the torsional torque on the piston, ensuring that the piston's vertical stroke is purely linear. Because the anti-rotation mechanism is a built-in design, there is no need to add an additional anti-rotation baffle outside the bracket. The overall actuator height no longer increases as the need for torsional protection increases, saving vertical installation space, simplifying the number of parts, and reducing manufacturing and assembly costs. The elimination of torsional loads reduces lateral wear on the piston, guide assembly, and seals, reduces fatigue damage to structural components, and significantly extends the service life of the cylinder and the maintenance cycle of the valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying creative labor, other drawings obtained based on these drawings still fall within the scope of the present invention.

[0018] Figure 1 It is a structural diagram of the utility model;

[0019] Figure 2 This is a structural diagram of the piston in the present invention in a compressed state;

[0020] Figure 3 It is a structural diagram of the spring combination;

[0021] In the figure, 1. connecting base; 11. second fixing hole; 12. air outlet channel; 2. cylinder; 21. mounting cavity; 3. cylinder head; 31. first fixing hole; 32. air inlet channel; 4. piston; 41. through hole; 42. first O-ring; 43. second O-ring; 44. guide ring; 5. spring assembly; 51. limit rod; 52. positioning sleeve; 53. spring; 6. output connecting shaft; 61. third O-ring; 62. indicator rod; 63. fourth O-ring; 7. anti-rotation shaft; 8. limit rod; 81. adjusting bolt. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in further detail below with reference to the accompanying drawings.

[0023] It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two non-identical entities or non-identical parameters with the same name. It can be seen that "first" and "second" are only for the convenience of expression and should not be understood as limitations on the embodiments of the present invention. Subsequent embodiments will not explain this one by one.

[0024] The directional and positional terms used in this invention, such as "upper," "lower," "front," "back," "left," "right," "inner," "outer," "top," "bottom," and "side," are used solely to refer to the directions or positions in the accompanying drawings. Therefore, the directional and positional terms used are intended to illustrate and facilitate understanding of this invention and are not intended to limit the scope of protection of this invention.

[0025] like Figure 1-3 The figure shows an embodiment of a pneumatic actuator with a built-in anti-torsion spring return according to the present invention, comprising a connecting base 1, on which a cylinder 2 and a cylinder head 3 are provided. A mounting cavity 21 is provided within the cylinder 2, and a piston 4 assembly is mounted within the mounting cavity 21. The piston 4 assembly includes a spring 53 assembly 5 fixedly connected to the connecting base 1 at one end and connected to the piston 4 at the other end. An output connecting shaft 6 is provided within the cylinder 2, passing through the connecting base 1 and the piston 4. An anti-rotation shaft 7 is also provided within the mounting cavity 21. One end of the anti-rotation shaft 7 passes through the piston 4 and is fixed to the cylinder head 3, while the other end is fixed to the connecting base 1. When the piston 4 moves up and down, it will move linearly up and down along the anti-rotation shaft 7. The piston 4 will not rotate due to the torsion of the spring 53, completely eliminating the interference of the torsional torque on the piston 4, ensuring that the piston 4 moves purely linearly up and down. Because the anti-rotation mechanism is built-in, there's no need for an additional anti-rotation baffle on the bracket. As the need for torsional protection increases, the overall actuator height no longer increases, saving vertical installation space. This also simplifies the number of components and reduces manufacturing and assembly costs. The absence of torsional loads reduces lateral wear on the piston, guide assembly, and seals, minimizing fatigue damage to structural components. This significantly extends the cylinder's service life and valve maintenance intervals.

[0026] The cylinder head 3 is provided with a first fixing hole 31, the connecting base 1 is provided with a second fixing hole 11, and the piston 4 is provided with a through hole 41. The anti-rotation shaft 7 passes through through hole 41 and is fixed in the first fixing hole 31 and the second fixing hole 11. The first and second fixing holes 11 are aligned with the through hole 41 of the piston 4, and the anti-rotation shaft 7 is positioned by passing through the hole, eliminating the need for additional positioning parts and simplifying the assembly process. The positioning is achieved by directly drilling holes in the main body structure, eliminating additional processing and parts, reducing processing costs while maintaining a compact appearance.

[0027] There is at least one anti-rotation shaft 7. If there are two anti-rotation shafts 7, they are symmetrically arranged within the piston assembly 4. The symmetrical arrangement of the two anti-rotation shafts 7 provides a more balanced restraining torque during the return and compression of the spring 53, further improving the torsional resistance of large-stroke and large-diameter cylinders. While a single-axis solution can meet general specifications, a symmetrical dual-axis solution can be used in larger-diameter or higher-torque environments, providing flexible design options.

[0028] The outer periphery of the piston 4 is provided with a first O-ring 42 and a second O-ring 43 which are sealed to the cylinder 2. The double rings can be selected with different hardness or materials according to the pressure difference and temperature conditions of the medium, so as to achieve better sealing adaptation to different industrial working conditions (such as high temperature, high pressure, corrosive media).

[0029] A guide ring 44 is provided between the first O-ring 42 and the second O-ring 43. This ring abuts the inner wall of the cylinder 2, preventing the outer periphery of the piston 4 from contacting the inner wall. This ring provides lateral guidance, allowing the piston 4 to contact the cylinder 2 only via the ring, reducing frictional losses between the O-rings and the cylinder 2, and lowering energy consumption. The rigid ring 44 effectively prevents lateral swing of the piston 4, maintaining its concentricity and further ensuring smooth linear motion.

[0030] In this embodiment of the present application, unlike the aforementioned embodiment, an indicator rod 62 is connected to the output connecting shaft 6. The other end of the indicator rod 62 extends out of the cylinder head 3 to indicate the position of the valve or piston 4. The exposed position of the indicator rod 62 allows for quick determination of the current opening of the valve or piston 4, avoiding blind operation or misjudgment on site. During installation, commissioning, and routine inspections, the stroke position can be observed without disassembling the flange or blind hole, improving work efficiency.

[0031] The output connecting shaft 6 and indicator rod 62 are respectively fitted with a third O-ring 61 for sealing against the piston 4 and a fourth O-ring 63 for sealing against the cylinder head 3. The third O-ring ensures airtightness between the output connecting shaft 6 and the piston 4 assembly, preventing leakage of the medium at the shaft hole. The fourth O-ring forms a stable seal where the indicator rod 62 passes through the cylinder head 3, preventing external dust or liquid from entering the cavity. The double-end sealing design ensures a clean and dry working environment inside the actuator, reducing seal aging or damage caused by contaminants or lubricant leakage. With the output connecting shaft 6 and indicator rod 62 double-end sealed, internal cylinder pressure fluctuations have no external impact, and the indicator structure is also protected from medium corrosion, promoting long-term stable operation.

[0032] The spring assembly 53 includes a limiting rod 851, with positioning sleeves 52 provided at both ends. The positioning sleeves 52 are externally sleeved with a spring 53, which is compressed to a preloaded height by the positioning sleeves 52. The positioning sleeves 52 precisely control the initial compression of the spring 53, ensuring that the spring 53 is always in the designed preloaded state, ensuring a consistent and reliable reset force. Once the preload height is fixed, the spring 53 will not produce axial play due to vibration during the reciprocating motion of the piston 4, thus preventing abnormal noise and loosening. By replacing the positioning sleeves 52 with different lengths or diameters, the preload force can be flexibly adjusted without having to replace the entire set of springs 53, thus reducing maintenance costs.

[0033] The connecting base 1 is provided with a limit rod 851. One end of the limit rod 851 extends into the piston 4 assembly, and the other end is adjusted by an adjusting bolt 81 to adjust the height of the limit rod 851 within the piston 4 assembly. By adjusting the bolt 81, the upper and lower limit positions of the piston 4 movement can be precisely set, adapting to different stroke requirements without replacing parts. If the valve seal or stroke requirements change, simply loosen the adjusting bolt 81 and reposition the limit rod 851 to quickly complete the calibration and reduce downtime. The set height of the limit rod 851 protects the piston 4 and internal components from overtravel shock, extending component life and improving system safety.

[0034] The cylinder head 3 is provided with an air inlet passage 32 communicating with the mounting cavity 21, and the connecting base 1 is provided with an air outlet passage 12 communicating with the piston 4 assembly. The inlet and outlet passages are arranged axially, enabling direct communication between the air source and the piston 4 chamber, resulting in low airflow resistance and high ventilation efficiency. The inlet passage 32 directly connects to the mounting cavity 21, while the outlet passage 12 directly reaches the lower chamber of the piston 4, shortening the air inlet and outlet paths and enabling faster and more sensitive opening and closing of the actuator.

[0035] The above disclosure is only a preferred embodiment of the present invention, and certainly cannot be used to limit the scope of rights of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope covered by the present invention.

[0036] Although the present invention has been described with reference to several specific embodiments, it should be understood that the present invention is not limited to the specific embodiments disclosed, and the present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A linear pneumatic actuator with a built-in anti-torsion spring return, characterized by: It includes a connecting base, a cylinder and a cylinder head are provided on the connecting base, a mounting cavity is provided inside the cylinder, a piston assembly is installed in the mounting cavity, the piston assembly includes a spring combination fixedly connected to the connecting base at one end, and a piston is connected at the other end, an output connecting shaft is provided in the cylinder that passes through the connecting base and the piston, an anti-rotation shaft is also provided in the mounting cavity, one end of the anti-rotation shaft passes through the piston and is fixed on the cylinder head, and the other end is fixed in the connecting base.

2. The linear pneumatic actuator with built-in anti-torsion spring return according to claim 1, characterized in that: The cylinder cover is provided with a first fixing hole, the connecting base is provided with a second fixing hole, the piston is provided with a through hole, and the anti-rotation shaft passes through the through hole and is fixed in the first fixing hole and the second fixing hole.

3. The linear pneumatic actuator with built-in anti-torsion spring return according to claim 2, characterized in that: The number of the anti-rotation shaft is at least one. When the number of the anti-rotation shaft is two, the anti-rotation shafts are symmetrically arranged in the piston assembly.

4. The linear pneumatic actuator with built-in anti-torsion spring return according to claim 1, characterized in that: The outer periphery of the piston is provided with a first O-ring and a second O-ring which are sealed with the cylinder.

5. The linear pneumatic actuator with built-in anti-torsion spring return according to claim 4, characterized in that: A guide ring is provided between the first O-ring and the second O-ring, and the guide ring is used to abut against the inner wall of the cylinder so that the outer periphery of the piston does not contact the inner wall of the cylinder.

6. The linear pneumatic actuator with built-in anti-torsion spring return according to claim 1, characterized in that: The output connecting shaft is connected to an indicator rod, and the other end of the indicator rod extends out of the cylinder cover to indicate the position of the valve or piston switch.

7. The linear pneumatic actuator with built-in anti-torsion spring return according to claim 6, characterized in that: The output connecting shaft and the indicator rod outer sleeve are respectively covered with a third O-ring for sealing with the piston and a fourth O-ring for sealing with the cylinder cover.

8. The linear pneumatic actuator with built-in anti-torsion spring return according to claim 1, characterized in that: The spring assembly includes a limiting rod, and positioning sleeves are provided at both ends of the limiting rod. A spring is sleeved on the outside of the positioning sleeve, and the spring is compressed to a pre-tightened compression height by the positioning sleeve.

9. The linear pneumatic actuator with built-in anti-torsion spring return according to claim 1, characterized in that: A limiting rod is provided on the connecting base, one end of the limiting rod extends into the piston assembly, and the other end is used to adjust the height of the limiting rod in the piston assembly through an adjusting bolt.

10. The linear pneumatic actuator with built-in anti-torsion spring return according to claim 1, characterized in that: The cylinder cover is provided with an air inlet passage communicating with the mounting cavity, and the connecting base is provided with an air outlet passage communicating with the piston assembly.

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