Airtightness detection rotating oil cylinder

Abstract

The utility model discloses an air tightness detection rotary oil cylinder, which belongs to the technical field of rotary oil cylinders and comprises a shell, a piston component and an air tightness detection component are mounted on the inner side of the shell, the air tightness detection component is connected with the piston component, and sealing components are mounted on the shell, the piston component and the air tightness detection component. The air tightness detection assembly comprises an end cover and an O-shaped ring F. The end cover is installed on the inner side of the lower end of the shell, the upper end of the end cover extends to the inner side of the lower end of the piston assembly, the O-shaped ring F is installed on the inner side of the piston assembly, and the inner side of the O-shaped ring F is slidably connected with the end cover. A through hole is formed in the middle of the end cover so that a cavity between the end cover and the piston assembly can be communicated with the outer side. Air tightness detection equipment is arranged on the outer side of the through hole of the end cover. Through the mode, the air path between the upper end of the end cover and the piston assembly is detected through the air tightness detection equipment, so that the operation state of the piston assembly can be accurately detected, and the stability of subsequent processing is facilitated.

Description

TECHNICAL FIELD

[0001] The utility model relates to rotary oil cylinder technical field, concretely relates to air tightness detection rotary oil cylinder. BACKGROUND

[0002] Rotary oil cylinder is a kind of hydraulic element, mainly used to realize rotary motion, drives piston or rotating shaft by the pressure action of hydraulic oil, to realize the rotation of object, and rotary oil cylinder is widely used in mechanical equipment, engineering machinery, automation equipment and other fields.

[0003] For example, Chinese patent application CN115234536A discloses a rotary oil cylinder, which comprises a piston rod, a cylinder cover, a cylinder body and a guide column. The cylinder cover is inserted into the cylinder body and fixedly connected with the cylinder body. A spiral track is formed on the cylinder cover. The guide column is inserted into the piston rod. When the combination of the cylinder cover and the cylinder body moves, the guide column moves along the spiral track to generate a rotary torque on the piston rod.

[0004] However, the rotary oil cylinder cannot accurately detect the running state of the equipment.

[0005] Therefore, the utility model designs air tightness detection rotary oil cylinder to solve the above problems. UTILITY MODEL CONTENTS

[0006] In view of the above shortcomings of the prior art, the utility model provides air tightness detection rotary oil cylinder.

[0007] To achieve the above purpose, the utility model realizes the following technical scheme:

[0008] The air tightness detection rotary oil cylinder comprises an outer shell,

[0009] The outer shell is internally provided with a piston assembly and an air tightness detection assembly, the air tightness detection assembly is connected with the piston assembly, and a sealing assembly is installed on the outer shell, the piston assembly and the air tightness detection assembly;

[0010] The air tightness detection assembly comprises an end cover and an O-ring F. The upper end of the end cover is in a cylindrical shape. The top end of the end cover is provided with a protrusion. The lower end of the end cover is in a disc shape. The outer side of the disc of the end cover is provided with an annular protrusion. The end cover is installed on the inner side of the lower end of the outer shell. The upper end of the end cover extends to the inner side of the lower end of the piston assembly. The O-ring F is installed on the inner side of the piston assembly. The inner side of the O-ring F is slidably connected with the end cover. A through hole is formed in the middle of the end cover to communicate the cavity between the end cover and the piston assembly with the outside. The through hole of the end cover is provided with an air tightness detection device.

[0011] Further, the shell comprises a cylinder, a limiting sleeve, a cover plate, bolts, a steel ball, two plugs and a ball plug, the upper end of the limiting sleeve is inserted into the inner side of the lower end of the cylinder, the cover plate is located at the lower end of the limiting sleeve, a plurality of bolts pass through the cover plate, the limiting sleeve and the cylinder in sequence to fixedly connect the cover plate and the limiting sleeve and the limiting sleeve and the cylinder, the bolts are in threaded connection with the cover plate, the limiting sleeve and the cylinder, the lower end of the end cover is in abutting connection with the cover plate and the limiting sleeve, the steel ball is located in the inner side of the limiting sleeve and is in rolling connection with the cylinder and the limiting sleeve, the two plugs are sealingly and fixedly installed on the outer side of the cylinder, the ball plug is sealingly installed on the upper end of the cylinder, the inner sides of the cylinder, the limiting sleeve and the steel ball are connected with the piston assembly.

[0012] Further, the piston assembly comprises a piston rod, a square ring A for hole, a square ring B for hole and a positioning pin, the piston rod is in sliding connection with the inner side of the cylinder, the lower end of the piston rod is in sliding connection with the inner side of the limiting sleeve, the lower end of the piston rod is provided with a deep groove for accommodating the upper end of the end cover and is in sliding connection with the end cover, the middle section of the piston rod is provided with an annular protrusion, a cavity is formed between the upper end of the annular protrusion of the piston rod and the cylinder, a spiral groove for matching the steel ball is formed on the outer side of the lower end of the annular protrusion of the piston rod, the steel ball is located in the spiral groove of the piston rod and is in rolling connection with the piston rod, the square ring A for hole is sealingly and fixedly installed on the outer side of the lower end of the piston rod, the outer side of the square ring A for hole is in sealing abutting connection with the limiting sleeve, the square ring B for hole is sealingly and fixedly installed on the outer side of the middle section annular protrusion of the piston rod, the outer side of the square ring B for hole is in sealing sliding connection with the cylinder, and the positioning pin is fixedly installed on the upper end of the piston rod.

[0013] Further, the sealing assembly comprises a dustproof ring, O-rings A, B and C, two O-rings D, two O-rings E and a stepped ring for shaft, the dustproof ring is located between the cylinder and the piston rod, the outer side of the dustproof ring is in sealing fixed connection with the cylinder, the inner side of the dustproof ring is in sealing sliding connection with the piston rod, the O-ring A is sealingly and fixedly installed between the middle sections of the cylinder and the limiting sleeve, the O-ring B is sealingly and fixedly installed between the limiting sleeve and the end cover, the O-ring C is sealingly and fixedly installed between the lower ends of the cylinder and the limiting sleeve, the two O-rings D are sleeved on the outer side of the cylinder and are in abutting connection with the cylinder, the two O-rings E are in sealing fixed connection with the cylinder, the stepped ring for shaft is sealingly and fixedly installed on the inner side of the upper end of the cylinder, and the inner side of the square ring B for hole is in sealing sliding connection with the piston rod.

[0014] Further, the upper end of the limiting sleeve is in a cylindrical shape, the lower end of the limiting sleeve is in a disc shape, an annular groove is formed between the cover plate and the limiting sleeve, and the disc outer side annular protrusion of the end cover is located in the annular groove between the cover plate and the limiting sleeve.

[0015] Furthermore, the upper end of the cylinder body is provided with through groove A and through groove B, and two plugs are respectively located in through groove A and through groove B. The lower ends of through groove A and through groove B are provided with channels to communicate with the outside. Two O-rings E are respectively located at the lower ends of the two channels. Through groove A is connected to the cavity between the lower end of the annular protrusion of the piston rod, the cylinder body and the upper end of the limiting sleeve. Through groove B is connected to the cavity between the upper end of the annular protrusion of the piston rod and the cylinder body. The upper end of through groove B is connected to the outside through a channel. A ball plug is sealed and engaged in the channel at the upper end of through groove B.

[0016] Furthermore, a channel is provided on one side of the cylinder body and the limiting sleeve to connect the cavity between the piston rod and the end cover with the outside. O-ring A is located on the upper inner side of the channel of the cylinder body, O-ring B and O-ring C are located on the lower ends of the channel of the limiting sleeve, and two O-rings D are located on the upper and lower outer sides of the channel of the cylinder body.

[0017] Furthermore, the positioning pin has a through hole for positioning purposes.

[0018] Compared with the prior art, the advantages of this utility model are as follows: 1. By using an airtightness testing device to test the air passage between the upper end of the end cap and the piston assembly, the operating status of the piston assembly can be accurately detected, which facilitates the stability of subsequent processing.

[0019] 2. The channel on one side of the cylinder and the limiting sleeve ensures that the cavity between the upper end of the end cover and the piston rod can be connected to the outside air when not in operation, thus ensuring the accuracy of the airtightness testing equipment. The use of multiple O-rings ensures the complete sealing of the entire equipment. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a perspective view of the rotary hydraulic cylinder for airtightness testing according to this utility model;

[0022] Figure 2 This is a front view of the rotary hydraulic cylinder for airtightness testing according to this utility model;

[0023] Figure 3 This is a left view of the rotary hydraulic cylinder for airtightness testing according to this utility model;

[0024] Figure 4 This is a top view of the rotary hydraulic cylinder for airtightness testing according to this utility model;

[0025] Figure 5 is a bottom view of the air tightness detection rotary oil cylinder of the utility model;

[0026] Figure 6 is a sectional view along A-A of Figure 3

[0027] Figure 7 is a sectional view along B-B of Figure 4

[0028] Figure 8 is a sectional view along C-C of Figure 4

[0029] Figure 9 is a sectional view along D-D of Figure 4

[0030] The reference numerals in the drawings represent respectively:

[0031] 1. cylinder body; 2. limiting sleeve; 3. piston rod; 4. end cover; 5. cover plate; 6. bolt; 7. steel ball; 8. plug; 81. through groove A; 82. through groove B; 9. ball plug; 10. dustproof ring; 11. O-ring A; 12. O-ring B; 13. O-ring C; 14. O-ring D; 15. O-ring E; 16. O-ring F; 17. square ring for hole A; 18. square ring for hole B; 19. stepped ring for shaft; 20. positioning pin. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme in the embodiments of the utility model will be described clearly and completely below in combination with the drawings in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the utility model.

[0033] In the following description, "left", "right", "front", "back", "upper", "lower" are oriented in the perspective direction of the front view.

[0034] In some embodiments, referring to the front view of the drawings in the description, Figures 1-9 The air tightness detection rotary oil cylinder comprises an outer shell,

[0035] The outer shell is internally provided with a piston assembly and an air tightness detection assembly, the air tightness detection assembly is connected with the piston assembly, and a sealing assembly is installed on the outer shell, the piston assembly and the air tightness detection assembly;

[0036] ​​​​The air tightness detection assembly comprises an end cover 4 and an O-shaped ring F16, the upper end of the end cover 4 is in a cylindrical shape, a protrusion is arranged at the top end of the end cover 4, the lower end of the end cover 4 is in a disc shape, an annular protrusion is arranged on the outer side of the disc of the end cover 4, the end cover 4 is installed on the inner side of the lower end of the shell, the upper end of the end cover 4 extends to the inner side of the lower end of the piston assembly, the O-shaped ring F16 is installed on the inner side of the piston assembly, the inner side of the O-shaped ring F16 is in sliding connection with the end cover 4, a through hole is arranged in the middle of the end cover 4 to make the cavity between the end cover 4 and the piston assembly in communication with the outside, and the through hole of the end cover 4 is provided with an air tightness detection device on the outside.

[0037] In normal use of the air tightness detection rotary oil cylinder, oil is injected between the shell and the piston assembly, so that the piston assembly moves upward and rotates under the limitation of the shell, the O-shaped ring F16 is driven by the piston assembly to move upward, the O-shaped ring F16 moves to be in contact with and sealed by the cylindrical protrusion of the end cover 4, a closed air passage is formed between the upper end of the end cover 4 and the piston assembly, and the air passage between the upper end of the end cover 4 and the piston assembly is detected by the air tightness detection device, so that the running state of the piston assembly can be accurately detected, and the stability of subsequent processing is facilitated.

[0038] The shell comprises a cylinder body 1, a limiting sleeve 2, a cover plate 5, bolts 6, a steel ball 7, two plugs 8 and a ball plug 9, the upper end of the limiting sleeve 2 is inserted into the inner side of the lower end of the cylinder body 1, the cover plate 5 is located at the lower end of the limiting sleeve 2, a plurality of bolts 6 are sequentially threaded through the cover plate 5, the limiting sleeve 2 and the cylinder body 1 to fixedly connect the cover plate 5 and the limiting sleeve 2 and the limiting sleeve 2 and the cylinder body 1, the bolts 6 are in threaded connection with the cover plate 5, the limiting sleeve 2 and the cylinder body 1, the lower end of the end cover 4 is in abutting connection with the cover plate 5 and the limiting sleeve 2, the steel ball 7 is located in the inner side of the limiting sleeve 2 and is in rolling connection with the cylinder body 1 and the limiting sleeve 2, the two plugs 8 are sealingly and fixedly installed on the outer side of the cylinder body 1, the ball plug 9 is sealingly installed on the upper end of the cylinder body 1, and the inner sides of the cylinder body 1, the limiting sleeve 2 and the steel ball 7 are connected with the piston assembly.

[0039] The piston assembly comprises a piston rod 3, a square hole ring A 17, a square hole ring B 18 and a positioning pin 20, the piston rod 3 is in sliding connection with the inner side of the cylinder body 1, the lower end of the piston rod 3 is in sliding connection with the inner side of the limiting sleeve 2, a deep groove accommodating the upper end of the end cover 4 is arranged at the lower end of the piston rod 3 and is in sliding connection with the end cover 4, an annular protrusion is arranged in the middle of the piston rod 3, a cavity is formed between the upper end of the annular protrusion of the piston rod 3 and the cylinder body 1, a spiral groove matched with the steel ball 7 is arranged on the outer side of the lower end of the annular protrusion of the piston rod 3, the steel ball 7 is located in the spiral groove of the piston rod 3 and is in rolling connection with the piston rod 3, the square hole ring A 17 is sealingly and fixedly installed on the outer side of the lower end of the piston rod 3, the outer side of the square hole ring A 17 is in sealing abutting connection with the limiting sleeve 2, the square hole ring B 18 is sealingly and fixedly installed on the outer side of the annular protrusion in the middle of the piston rod 3, the outer side of the square hole ring B 18 is in sealing sliding connection with the cylinder body 1, and the positioning pin 20 is fixedly installed on the upper end of the piston rod 3.

[0040] The sealing assembly comprises a dustproof ring 10, an O-ring A11, an O-ring B12, an O-ring C13, two O-rings D14, two O-rings E15 and a stepped ring 19 for shaft, the dustproof ring 10 is located between the cylinder body 1 and the piston rod 3, the outer side of the dustproof ring 10 is sealingly and fixedly connected with the cylinder body 1, the inner side of the dustproof ring 10 is sealingly and slidingly connected with the piston rod 3, the O-ring A11 is sealingly and fixedly installed between the cylinder body 1 and the middle section of the limiting sleeve 2, the O-ring B12 is sealingly and fixedly installed between the limiting sleeve 2 and the end cover 4, the O-ring C13 is sealingly and fixedly installed between the cylinder body 1 and the lower end of the limiting sleeve 2, the two O-rings D14 are sleeved on the outer side of the cylinder body 1 and are in abutting connection with the cylinder body 1, the two O-rings E15 are sealingly and fixedly connected with the cylinder body 1, the stepped ring 19 for shaft is sealingly and fixedly installed on the inner side of the upper end of the cylinder body 1, and the inner side of the square ring B18 is sealingly and slidingly connected with the piston rod 3.

[0041] The upper end of the limiting sleeve 2 is in a cylindrical shape, the lower end of the limiting sleeve 2 is in a disc shape, the annular groove is formed between the cover plate 5 and the limiting sleeve 2, and the disc outer side annular protrusion of the end cover 4 is located in the annular groove between the cover plate 5 and the limiting sleeve 2.

[0042] The upper end of the cylinder body 1 is provided with a through groove A81 and a through groove B82, two plugs 8 are located in the through groove A81 and the through groove B82 respectively, the lower end of the through groove A81 and the through groove B82 is provided with a channel in communication with the outside, the two O-rings E15 are located at the lower end of the two channels respectively, the through groove A81 is in communication with the cavity between the lower end of the annular protrusion of the piston rod 3, the upper end of the cylinder body 1 and the limiting sleeve 2, the through groove B82 is in communication with the cavity between the upper end of the annular protrusion of the piston rod 3 and the cylinder body 1, the upper end of the through groove B82 is in communication with the outside through the channel, and the ball plug 9 is sealingly and clamped in the channel at the upper end of the through groove B82.

[0043] The cylinder body 1 and the limiting sleeve 2 are provided with a channel on one side to make the cavity between the piston rod 3 and the end cover 4 in communication with the outside, the O-ring A11 is located above the inner side of the channel of the cylinder body 1, the O-ring B12 and the O-ring C13 are located below the two ends of the channel of the limiting sleeve 2 respectively, and the two O-rings D14 are located above and below the outer side of the channel of the cylinder body 1 respectively.

[0044] The positioning pin 20 is provided with a through hole for positioning.

[0045] The airtight detection rotary oil cylinder is normally used, oil is injected from the lower end passage of the through groove B82, the oil enters below the annular protrusion of the piston rod 3 through the passage, the oil drives the piston rod 3 to move upwards, the O-ring A11, the square hole ring A17 and the square hole ring B18 are arranged to avoid oil leakage, the piston rod 3 drives the O-ring F16 to move, the O-ring F16 moves to contact and seal with the cylindrical protrusion of the end cover 4, so that the airtight detection equipment detects the closed air circuit, oil is injected from the lower end passage of the through groove A81, the oil enters above the annular protrusion of the piston rod 3 through the passage, the oil drives the piston rod 3 to move downwards, the stepped ring 19 arranged for the shaft avoids oil leakage, the piston rod 3 drives the O-ring F16 to move, the O-ring F16 is separated from the contact with the cylindrical protrusion of the end cover 4, the passage on one side of the cylinder body 1 and the limiting sleeve 2 is communicated with the upper end cavity of the end cover 4, and the closed air circuit is no longer formed, the O-ring B12, the O-ring C13 and the O-ring D14 are arranged to ensure that the air circuit is unobstructed, so as to avoid gas leakage, the dustproof ring 10 is arranged to avoid dust and sundries from entering the inside of the cylinder body 1 to affect the operation of the equipment, the cavity between the upper end of the end cover 4 and the piston rod 3 is communicated with the outside air in the non-operating state through the passage on one side of the cylinder body 1 and the limiting sleeve 2, so as to ensure the accuracy of the airtight detection equipment, and the sealing integrity of the whole equipment is ensured through the arrangement of the plurality of O-rings.

[0046] The above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements will not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A rotary hydraulic cylinder for airtightness testing, including a housing, characterized in that: A piston assembly and an airtightness detection assembly are installed inside the housing. The airtightness detection assembly is connected to the piston assembly. Sealing assemblies are installed on the housing, the piston assembly, and the airtightness detection assembly. The airtightness testing component includes an end cap (4) and an O-ring F (16). The upper end of the end cap (4) is cylindrical, and a protrusion is provided at the top of the cylinder of the end cap (4). The lower end of the end cap (4) is disc-shaped, and an annular protrusion is provided on the outer side of the disc of the end cap (4). The end cap (4) is installed on the inner side of the lower end of the outer shell. The upper end of the end cap (4) extends to the inner side of the lower end of the piston assembly. The O-ring F (16) is installed on the inner side of the piston assembly. The inner side of the O-ring F (16) is slidably connected to the end cap (4). A through hole is provided in the middle of the end cap (4) to communicate with the cavity between the end cap (4) and the piston assembly and the outside. An airtightness testing device is provided on the outer side of the through hole of the end cap (4).

2. The rotary hydraulic cylinder for airtightness testing according to claim 1, characterized in that, The outer casing includes a cylinder body (1), a limiting sleeve (2), a cover plate (5), bolts (6), a steel ball (7), two plugs (8), and a ball plug (9). The upper end of the limiting sleeve (2) is inserted into the inner side of the lower end of the cylinder body (1). The cover plate (5) is located at the lower end of the limiting sleeve (2). Multiple bolts (6) pass through the cover plate (5), the limiting sleeve (2), and the cylinder body (1) in sequence to fix the cover plate (5) and the limiting sleeve (2), and the limiting sleeve (2) and the cylinder body (1) in a fixed connection. (6) is threadedly connected to the cover plate (5), the limiting sleeve (2) and the cylinder (1). The lower end of the end cap (4) is in contact with the cover plate (5) and the limiting sleeve (2). The steel ball (7) is located inside the limiting sleeve (2) and is in rolling connection with the cylinder (1) and the limiting sleeve (2). Two plugs (8) are sealed and fixedly installed on the outside of the cylinder (1). The ball plug (9) is sealed and installed on the upper end of the cylinder (1). The cylinder (1), the limiting sleeve (2) and the steel ball (7) are connected to the piston assembly.

3. The rotary hydraulic cylinder for airtightness testing according to claim 2, characterized in that, The piston assembly includes a piston rod (3), a square ring A (17) for bores, a square ring B (18) for bores, and a positioning pin (20). The piston rod (3) is slidably connected to the inner side of the cylinder body (1). The lower end of the piston rod (3) is slidably connected to the inner side of the limiting sleeve (2). The lower end of the piston rod (3) has a deep groove for receiving the upper end of the end cap (4) and is slidably connected to the end cap (4). The middle section of the piston rod (3) is provided with an annular protrusion. A cavity is formed between the upper end of the annular protrusion of the piston rod (3) and the cylinder body (1). The outer side of the lower end of the annular protrusion of the piston rod (3) is opened. A spiral groove is provided for use with a steel ball (7). The steel ball (7) is located in the spiral groove of the piston rod (3) and is in rolling connection with the piston rod (3). A square ring A (17) is fixedly and sealed on the outer side of the lower end of the piston rod (3). The outer side of the square ring A (17) is in sealing contact with the limiting sleeve (2). A square ring B (18) is fixedly and sealed on the outer side of the annular protrusion in the middle section of the piston rod (3). The outer side of the square ring B (18) is in sealing sliding connection with the cylinder body (1). A positioning pin (20) is fixedly installed on the upper end of the piston rod (3).

4. The rotary hydraulic cylinder for airtightness testing according to claim 3, characterized in that, The sealing assembly includes a dust seal (10), an O-ring A (11), an O-ring B (12), an O-ring C (13), two O-rings D (14), two O-rings E (15), and a stepped ring for the shaft (19). The dust seal (10) is located between the cylinder body (1) and the piston rod (3). The outer side of the dust seal (10) is sealed and fixedly connected to the cylinder body (1), and the inner side of the dust seal (10) is sealed and slidably connected to the piston rod (3). The O-ring A (11) is sealed and fixedly installed in the cylinder body (1) and the limiting sleeve (2). Between the segments, O-ring B (12) is sealed and fixed between the limiting sleeve (2) and the end cover (4), O-ring C (13) is sealed and fixed between the cylinder body (1) and the lower end of the limiting sleeve (2), two O-rings D (14) are fitted on the outside of the cylinder body (1) and abut against the cylinder body (1), two O-rings E (15) are sealed and fixed to the cylinder body (1), the shaft is sealed and fixed to the inner side of the upper end of the cylinder body (1) with a stepped ring (19), and the hole is sealed and slidably connected to the piston rod (3) with the inner side of the square ring B (18).

5. The rotary hydraulic cylinder for airtightness testing according to claim 4, characterized in that, The upper end of the limiting sleeve (2) is cylindrical, and the lower end of the limiting sleeve (2) is disc-shaped. An annular groove is formed between the cover plate (5) and the limiting sleeve (2). The annular protrusion on the outer side of the disc of the end cap (4) is located in the annular groove between the cover plate (5) and the limiting sleeve (2).

6. The rotary hydraulic cylinder for airtightness testing according to claim 5, characterized in that, The cylinder body (1) has a through groove A (81) and a through groove B (82) at its upper end. Two plugs (8) are located in the through groove A (81) and the through groove B (82) respectively. The lower ends of the through groove A (81) and the through groove B (82) are connected to the outside. Two O-rings E (15) are located at the lower ends of the two channels respectively. The through groove A (81) is connected to the cavity between the lower end of the annular protrusion of the piston rod (3) and the upper end of the cylinder body (1) and the limiting sleeve (2). The through groove B (82) is connected to the cavity between the upper end of the annular protrusion of the piston rod (3) and the cylinder body (1). The upper end of the through groove B (82) is connected to the outside through the channel. The ball plug (9) is sealed and snapped into the channel at the upper end of the through groove B (82).

7. The rotary hydraulic cylinder for airtightness testing according to claim 6, characterized in that, The cylinder (1) and the limiting sleeve (2) are provided with a channel on one side to connect the cavity between the piston rod (3) and the end cap (4) with the outside. O-ring A (11) is located on the upper inner side of the channel of the cylinder (1), O-ring B (12) and O-ring C (13) are located on the lower ends of the channel of the limiting sleeve (2), and two O-rings D (14) are located on the upper and lower outer sides of the channel of the cylinder (1).

8. The rotary hydraulic cylinder for airtightness testing according to claim 7, characterized in that, The positioning pin (20) has a through hole for positioning.

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