Socket wrench

Abstract

The utility model discloses a socket spanner, which relates to the technical field of maintenance tools and comprises a lengthened socket rod, a socket head and a claw hook. One end of the lengthened sleeve rod can be located outside equipment with a component to be dismounted, and the other end of the lengthened sleeve rod can be fixedly connected with the sleeve head. A bayonet is formed in the end, away from the lengthened sleeve rod, of the sleeve head and used for clamping a connecting piece to be dismounted. At least one mounting channel is formed in the circumferential inner wall of the bayonet, a clamping device is arranged in each mounting channel, each clamping device is provided with a telescopic end capable of elastically stretching out and drawing back, and the telescopic ends can abut against the outer side wall of the connecting piece located in the bayonet; and the grapnel is arranged on the lengthened sleeve rod and is provided with a hooking part. The personal safety risk is reduced, and safe operation of operators is guaranteed.

Description

Technical Field

[0001] The utility model relates to the technical field of maintenance tools, in particular to a socket wrench. Background Art

[0002] The internal medium of the adsorption tower of the Fischer-Tropsch synthesis hydrogen purification device (hereinafter referred to as the adsorption tower) is CO and hydrogen. When adsorbent needs to be added during the maintenance of the adsorption tower, the internal grille and internal components (grille fixing nuts) need to be removed. The existing removal method is that the operator uses ordinary disassembly tools to enter the adsorption tower to carry out the removal work.

[0003] Since ordinary disassembly tools are relatively short and cannot support personnel to remove the grille and internal components inside the adsorption tower outside the adsorption tower, the operator must enter the toxic gas environment (there are still certain toxic gases such as CO after the internal replacement of the adsorption tower) to work in order to remove the grille and internal components. Therefore, the personal safety risk to the operator is high. Summary of the Utility Model

[0004] The purpose of the utility model is to provide a socket wrench to solve the problems existing in the above-mentioned prior art, reduce the personal safety risk, and ensure the safe operation of the operator.

[0005] To achieve the above purpose, the utility model provides the following scheme:

[0006] The utility model provides a socket wrench, which includes an extended socket rod, a socket head and a hook; one end of the extended socket rod can be located outside the equipment of the component to be removed, and the other end of the extended socket rod can be fixedly connected with the socket head; a bayonet is arranged at one end of the socket head far away from the extended socket rod, and the bayonet is used for clamping the connecting piece to be removed; at least one installation channel is arranged on the circumferential inner wall of the bayonet, and a clamping device is arranged in each installation channel. The clamping device has an elastically telescopic end, and the elastically telescopic end can abut against the outer side wall of the connecting piece located in the bayonet; the hook is arranged on the extended socket rod, and the hook has a hooking part.

[0007] Preferably, the hook is rotatably connected to the extended socket rod.

[0008] Preferably, the clamping device includes a first elastic element and a first steel ball; the first elastic element and the first steel ball are both located in the installation channel, and the first elastic element is located on the side of the first steel ball far away from the bayonet; the installation channel is communicated with the bayonet through a communication port; the diameter of the first steel ball is larger than the diameter of the communication port, and a part of the first steel ball can protrude from the inner side wall of the bayonet; the first steel ball forms the telescopic end.

[0009] Preferably, a connecting cylinder is fixedly arranged on the outer side wall of the lengthened sleeve rod. The connecting cylinder has a sliding cavity and an opening communicating with the sliding cavity. One end of the hook opposite to the holding part is the first end, and a limiting part is fixedly arranged at the first end. The outer diameter of the limiting part is smaller than the inner diameter of the sliding cavity, and the outer diameter of the limiting part is larger than the inner diameter of the opening. The limiting part is located in the sliding cavity and can rotate around the axis of the sliding cavity. When the limiting part rotates around the axis of the sliding cavity, the holding part can change the holding orientation.

[0010] Preferably, a second elastic element is arranged in the sliding cavity on the side of the limiting part away from the opening. The second elastic element can elastically extrude the limiting part along a first direction and make the limiting part slide in the sliding cavity along the first direction. When the limiting part slides along the first direction, the holding part can approach or move away from the axis of the lengthened sleeve rod.

[0011] Preferably, a handle is fixedly arranged at one end of the lengthened sleeve rod away from the sleeve head.

[0012] Preferably, the material of the sleeve head is beryllium bronze.

[0013] Preferably, a limiting block is arranged at one end of the lengthened sleeve rod away from the handle, and a limiting groove matching the limiting block is arranged at the corresponding end of the sleeve head. When the limiting block is located in the limiting groove, the lengthened sleeve rod can drive the sleeve head to rotate synchronously around the axis of the lengthened sleeve rod.

[0014] Preferably, a through channel is arranged on the side wall of the limiting block, and a third elastic element is arranged in the through channel. Third steel balls are respectively arranged on the outer sides of both ends of the third elastic element. The outer diameter of the third steel ball is smaller than the inner diameter of the through channel, and the outer diameter of the third steel ball is larger than the inner diameter of the end opening of the through channel. The third steel ball can protrude from the outer side wall of the limiting block. Accommodating grooves are respectively arranged on the inner side wall of the limiting groove at positions corresponding to the third steel balls.

[0015] Preferably, the inside of the lengthened sleeve rod has a hollow cavity.

[0016] The utility model has achieved the following technical effects compared with the prior art:

[0017] The socket wrench provided by the utility model extends the socket head into the adsorption tower through the lengthened socket rod. At this time, the other end of the lengthened socket rod is located outside the adsorption tower. Therefore, it enables the operator not to enter the adsorption tower, reducing the harm to the operator caused by the toxic environment inside the adsorption tower. The socket head at the end of the lengthened socket rod can remove the grille fixing nut, and the clamping device inside the bayonet of the socket head can take out the removed grille fixing nut, reducing its falling into the adsorption tower. After all the grille fixing nuts are removed, the hook provided on the lengthened socket rod can hook and take out the grille. The whole disassembly process does not require manual entry into the adsorption tower, reducing the concentration of harmful gases in the environment where the operator works during disassembly, reducing the risk of personal safety, and ensuring the safe operation of the operator.

[0018] Further, the hook is rotatably connected to the lengthened socket rod, and it can change the hooking orientation of the hooking part, so as to be suitable for hooking and using different hooking parts.

[0019] Further, the clamping device adopts the method of the first elastic element abutting against the first steel ball. Its structure is simple, and when the connecting piece to be removed enters the bayonet, due to the spherical contact surface of the first steel ball, it can not only ensure its smooth entry into the bayonet, but also abut against the outer side wall of the connecting piece to be removed under the pressing action of the first elastic element. Based on its frictional force, the removed connecting piece can be stably located in the bayonet.

[0020] Further, the connecting cylinder is used in combination with the limiting part provided on the hook to realize the rotational connection of the hook, and its structure is simple and easy to manufacture.

[0021] Further, the second elastic element is arranged in combination with the sliding cavity, so as to realize the movement of the hook in the direction close to or away from the axis of the lengthened socket rod, so that the position where the hook can protrude relative to the axis direction of the lengthened socket rod can be changed. When it is necessary to remove the corresponding connecting piece in holes of different sizes, it has wide applicability. The inner wall of the hole can squeeze the hooking part of the hook inward, and at this time, the first elastic element can be synchronously compressed to make the overall outer diameter smaller.

[0022] Further, the setting of the handle can make the rotation of the lengthened socket rod more convenient, and can reduce the applied torque, making the disassembly easier.

[0023] Further, the socket head is made of beryllium bronze, which has high strength and hardness, can withstand high loads and frequent use; beryllium bronze is non-magnetic and will not generate sparks when impacted, and has higher safety in flammable, explosive and strong magnetic field environments; and it has excellent wear resistance and corrosion resistance, and is suitable for long-term use in harsh environments.

[0024] Furthermore, the matching arrangement of the limiting block and the limiting groove enables a stable connection between the lengthened sleeve rod and the sleeve head, ensuring the stability of synchronous rotation; and the detachable manner between the lengthened sleeve rod and the sleeve head is adopted, so that different sleeve heads or lengthened sleeve rods of different lengths can be replaced according to actual needs, thereby making it more applicable.

[0025] Furthermore, the third elastic element is matched with the third steel balls at both ends and the accommodating groove on the sleeve head, enabling the sleeve head to be stably connected to the lengthened sleeve rod and preventing the sleeve head from easily falling off the lengthened sleeve rod.

[0026] Furthermore, the lengthened sleeve rod is provided with a hollow interior, which can reduce the weight while ensuring the use strength, improve the lightweight level, and make it more convenient to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts.

[0028] Figure 1 It is a schematic diagram of the overall structure of the socket wrench provided by the present invention.

[0029] In the figure:

[0030] 100 - Socket wrench;

[0031] 10 - Lengthened sleeve rod; 11 - Handle; 12 - Limiting block; 121 - Through channel; 13 - Third elastic element; 14 - Third steel ball; 15 - Hollow cavity;

[0032] 20 - Sleeve head; 21 - Bayonet; 22 - Installation channel; 23 - Clamping device; 231 - First elastic element; 232 - First steel ball; 24 - Limiting groove; 25 - Accommodating groove;

[0033] 30 - Hook; 31 - Hook portion; 32 - Connecting cylinder; 321 - Sliding cavity; 33 - Limiting portion; 34 - Second elastic element. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0035] The purpose of the present utility model is to provide a socket wrench to solve the problems existing in the prior art, reduce the risk of personal safety, and ensure the safe operation of operators.

[0036] In order to make the above objects, features, and advantages of the present utility model more obvious and understandable, the present utility model will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0037] Embodiment 1

[0038] This embodiment provides a socket wrench 100, which is mainly but not limited to being used for removing the internal grille and grille fixing nuts of the adsorption tower in the Fischer-Tropsch synthesis hydrogen purification device. As Figure 1 shown, it includes an extended socket rod 10, a socket head 20, and a hook 30. One end of the extended socket rod 10 can be located outside the equipment of the component to be removed, and the other end of the extended socket rod 10 can be fixedly connected to the socket head 20. A bayonet 21 is provided at one end of the socket head 20 away from the extended socket rod 10. The bayonet 21 is used to hold the connecting piece to be removed (such as the grille fixing nut). At least one installation channel 22 is provided on the circumferential inner wall of the bayonet 21, and a clamping device 23 is provided in each installation channel 22. The clamping device 23 has an elastic telescopic end, and the telescopic end can abut against the outer side wall of the connecting piece located in the bayonet 21. The hook 30 is provided on the extended socket rod 10, and the hook 30 has a hooking portion 31.

[0039] By extending the socket head 20 into the adsorption tower through the extended socket rod 10, at this time, the other end of the extended socket rod 10 is located outside the adsorption tower. Therefore, it is possible to prevent the operator from entering the adsorption tower, reducing the harm of the toxic environment inside the adsorption tower to the operator. The socket head 20 at the end of the extended socket rod 10 can remove the grille fixing nut, and the clamping device 23 inside the bayonet 21 of the socket head 20 can take out the removed grille fixing nut, reducing its falling into the adsorption tower. After all the grille fixing nuts are removed, the hook 30 provided on the extended socket rod 10 can hook and take out the grille. The entire disassembly process does not require the operator to enter the adsorption tower, reducing the concentration of harmful gases in the environment where the operator performs the disassembly work, reducing the risk of personal safety, and ensuring the safe operation of the operator.

[0040] Specifically, the shape of the bayonet 21 of the socket head 20 matches the outer shape of the corresponding connector to be removed. For example, if the connector to be removed is a hex nut, the cross-section of the bayonet 21 of the socket head 20 is a corresponding hexagon.

[0041] Among them, regarding other related settings of the extension socket rod 10:

[0042] In an alternative embodiment of the present invention, preferably, as Figure 1 shown, a handle 11 is fixedly provided at one end of the extension socket rod 10 away from the socket head 20. The setting of the handle 11 can make the rotation of the extension socket rod 10 more convenient, and can reduce the applied torque, making the disassembly easier.

[0043] In an alternative embodiment of the present invention, preferably, as Figure 1 shown, the inside of the extension socket rod 10 has a hollow cavity 15. The extension socket rod 10 is provided with a hollow interior, which can reduce the weight while ensuring the use strength, improve the level of light weight, and make it more convenient to use.

[0044] Specifically, the length of the extension socket rod 10 can be set according to actual conditions, such as being set to 1300 mm.

[0045] Specifically, the shape of the handle 11 can be any one, such as the handle 11 cooperating with the extension socket rod 10 to form a T shape.

[0046] Among them, regarding other related settings of the grappling hook 30:

[0047] In an alternative embodiment of the present invention, preferably, as Figure 1 shown, the grappling hook 30 is rotatably connected to the extension socket rod 10. The grappling hook 30 is connected to the extension socket rod 10 in a rotatable manner, which can change the grappling orientation of the grappling portion 31, so as to be suitable for grappling use in different positions of the grappling portion 31.

[0048] In an alternative embodiment of the present invention, preferably, as Figure 1 shown, a connecting cylinder 32 is fixedly provided on the outer side wall of the extension socket rod 10. The connecting cylinder 32 has a sliding cavity 321 and an opening communicating with the sliding cavity 321; one end of the grappling hook 30 opposite to the grappling portion 31 is the first end, and a limiting portion 33 is fixedly provided at the first end. The outer diameter of the limiting portion 33 is smaller than the inner diameter of the sliding cavity 321, and the outer diameter of the limiting portion 33 is larger than the inner diameter of the opening; the limiting portion 33 is located in the sliding cavity 321, and the limiting portion 33 can rotate around the axis of the sliding cavity 321; when the limiting portion 33 rotates around the axis of the sliding cavity 321, the grappling portion 31 can change the grappling orientation. The rotation connection of the grappling hook 30 is realized by using the connecting cylinder 32 in cooperation with the limiting portion 33 provided on the grappling hook 30, and its structure is simple and easy to manufacture.

[0049] In an alternative embodiment of the present embodiment, preferably, as Figure 1 shown, a second elastic element 34 is disposed in a sliding cavity 321 on a side of the limiting portion 33 away from the opening. The second elastic element 34 can elastically press the limiting portion 33 in the first direction and cause the limiting portion 33 to slide in the sliding cavity 321 in the first direction. When the limiting portion 33 slides in the first direction, the hooking portion 31 can approach or move away from the axis of the extended sleeve rod 10. The provided second elastic element 34 is combined with the sliding cavity 321, so as to realize that the hook 30 can move in a direction close to or away from the axis of the extended sleeve rod 10, so that the position where the hook 30 can protrude relative to the axis direction of the extended sleeve rod 10 is variable. When it is necessary to remove corresponding connecting parts in holes of different sizes, the applicability is wide. The inner wall of the hole can press the hooking portion 31 of the hook 30 inward. At this time, the first elastic element 231 can be synchronously compressed to make the overall outer diameter smaller.

[0050] Specifically, the first direction is coaxial with the axis direction of the connecting cylinder 32, and it can be a direction perpendicular to the axis of the extended sleeve rod 10.

[0051] Among them, regarding other related settings of the sleeve head 20:

[0052] Specifically, the clamping device 23 includes but is not limited to the following specific structural settings, and it can also be any other existing structure that can clamp and fix the removed connecting part (such as a nut) in the bayonet 21.

[0053] Specifically, the number of the clamping devices 23 can be selected and set according to actual needs.

[0054] In an alternative embodiment of the present embodiment, preferably, as Figure 1 shown, the clamping device 23 includes a first elastic element 231 and a first steel ball 232. Both the first elastic element 231 and the first steel ball 232 are located in the installation channel 22. The first elastic element 231 is located on a side of the first steel ball 232 away from the bayonet 21. The installation channel 22 is communicated with the bayonet 21 through a communication port. The diameter of the first steel ball 232 is larger than the diameter of the communication port, and a part of the first steel ball 232 can protrude from the inner side wall of the bayonet 21. The first steel ball 232 forms a telescopic end. The clamping device 23 adopts the method of using the first elastic element 231 to abut against the first steel ball 232. Its structure is simple. When the connecting part to be removed enters the bayonet 21, due to the spherical contact surface of the first steel ball 232, it can not only ensure its smooth entry into the bayonet 21, but also abut against the outer side wall of the connecting part to be removed under the pressing action of the first elastic element 231. Based on its frictional force, the removed connecting part can be stably located in the bayonet 21.

[0055] In an alternative embodiment of the present example, preferably, the material of the socket head 20 is beryllium bronze. The socket head 20 made of beryllium bronze has high strength and hardness, can withstand high loads and frequent use; beryllium bronze is non-magnetic and will not generate sparks when impacted, and has higher safety in flammable, explosive and strong magnetic field environments; and it has excellent wear resistance and corrosion resistance, suitable for long-term use in harsh environments.

[0056] Specifically, the limiting groove 24 at one end of the socket head 20 and the bayonet 21 at the other end of the socket head 20 can be set to a connected state or a non-connected state, and relevant settings can be made according to actual needs.

[0057] Among them, regarding the connection structure setting of the extension socket rod 10 and the socket head 20:

[0058] In an alternative embodiment of the present example, preferably, as Figure 1 shown, a limiting block 12 is provided at one end of the extension socket rod 10 away from the handle 11, and a limiting groove 24 matching the limiting block 12 is provided at the corresponding end of the socket head 20; when the limiting block 12 is located in the limiting groove 24, the extension socket rod 10 can drive the socket head 20 to rotate synchronously around the axis of the extension socket rod 10. The matching setting of the limiting block 12 and the limiting groove 24 can stably connect the extension socket rod 10 and the socket head 20 and ensure the stability of synchronous rotation; and the extension socket rod 10 and the socket head 20 can be disassembled, and different socket heads 20 or extension socket rods 10 with different lengths can be replaced according to actual needs, so that its applicability is wider.

[0059] Specifically, the shapes of the limiting block 12 and the limiting groove 24 can be any shape that can keep the two rotating synchronously, such as the cross-section of the common limiting block 12 is square.

[0060] In an alternative embodiment of the present example, preferably, as Figure 1 shown, a through channel 121 is provided on the side wall of the limiting block 12, a third elastic element 13 is provided in the through channel 121, third steel balls 14 are respectively provided on the outer sides of both ends of the third elastic element 13, the outer diameter of the third steel ball 14 is smaller than the inner diameter of the through channel 121, and the outer diameter of the third steel ball 14 is larger than the inner diameter of the end opening of the through channel 121; the third steel ball 14 can protrude from the outer side wall of the limiting block 12; receiving grooves 25 are respectively provided on the inner side wall of the limiting groove 24 at the positions corresponding to the third steel balls 14. The third elastic element 13 is matched with the third steel balls 14 at both ends and the receiving grooves 25 on the socket head 20, so that the socket head 20 can be stably connected to the extension socket rod 10 and the socket head 20 is not easily detached from the extension socket rod 10.

[0061] Specifically, the accommodation groove 25 can be a single groove that matches the protruding part of a third steel ball 14, or an annular groove provided on the inner sidewall of the limit groove 24. At this time, after the lengthened sleeve rod 10 is inserted into the sleeve head 20 from any orientation, the protruding parts of the third steel balls 14 on the lengthened sleeve rod 10 can all be located in the annular groove.

[0062] Among them, regarding other relevant descriptions:

[0063] Specifically, taking the removal and use of the internal grille and grille fixing nuts of the Fischer-Tropsch synthesis hydrogen purification device adsorption tower as an example: After the maintenance personnel receive the adsorption tower maintenance task and remove the manhole at the top of the adsorption tower, at this time, the grille fixing nut is 800 mm away from the manhole opening. Due to the presence of CO toxic gas inside, ordinary tools cannot meet the on-site construction requirements. The socket wrench 100 of this embodiment (the length of the lengthened sleeve rod 10 is 1300 mm) can be used to remove the grille fixing nuts one by one. The clamping device 23 in the sleeve head 20 can keep the removed grille fixing nuts located in the bayonet 21. After all the grille fixing nuts are removed, use the grab hook 30 to hook and take out the grille.

[0064] Specifically, to improve the personal safety of the operator, when using the socket wrench 100 of this embodiment, corresponding protective devices such as protective clothing can also be worn.

[0065] Specifically, the lengthened sleeve rod 10 and the grab hook 30 can also be made of beryllium bronze to ensure the explosion-proof use effect.

[0066] Specifically, the first elastic element 231, the second elastic element 34, and the third elastic element 13 can be any existing part that can elastically deform and provide elastic force, such as a common spring.

[0067] In the present utility model, specific examples are used to elaborate on the principle and implementation manner of the present utility model. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present utility model; at the same time, for those of ordinary skill in the art, according to the idea of the present utility model, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present utility model.

Claims

1. A socket wrench, characterized in that: Includes extended socket rod, socket head and grab hook; One end of the extended sleeve rod can be located outside the device of the component to be removed, and the other end of the extended sleeve rod can be fixedly connected to the sleeve head; The end of the sleeve head away from the extended sleeve rod is provided with a bayonet, and the bayonet is used to clamp the connector to be removed; at least one mounting channel is provided on the circumferential inner wall of the bayonet, and a clamping device is provided in each mounting channel, and the clamping device has a retractable end that can be elastically retracted, and the retractable end can abut against the outer side wall of the connector located in the bayonet; The grab hook is arranged on the extended sleeve rod, and the grab hook has a hook holding portion.

2. The socket wrench according to claim 1, characterized in that: The grab hook is rotatably connected to the extended sleeve rod.

3. The socket wrench according to claim 1, characterized in that: The clamping device comprises a first elastic element and a first steel ball; the first elastic element and the first steel ball are both located in the installation channel, and the first elastic element is located on a side of the first steel ball away from the bayonet; The installation channel is connected to the bayonet through a connecting port; the diameter of the first steel ball is larger than the diameter of the connecting port, and part of the first steel ball can protrude from the inner wall of the bayonet; the first steel ball forms the telescopic end.

4. The socket wrench according to claim 2, characterized in that: A connecting tube is fixedly arranged on the outer side wall of the extended sleeve rod, and the connecting tube has a sliding cavity and an opening connected with the sliding cavity; the end of the grab hook opposite to the hook holding part is a first end, and a limiting part is fixedly arranged on the first end, and the outer diameter of the limiting part is smaller than the inner diameter of the sliding cavity, and the outer diameter of the limiting part is larger than the inner diameter of the opening; The limiting portion is located in the sliding cavity, and the limiting portion can rotate around the axis of the sliding cavity; when the limiting portion rotates around the axis of the sliding cavity, the hooking portion can change the hooking orientation.

5. The socket wrench according to claim 4, characterized in that: A second elastic element is disposed in the sliding cavity at a side of the limiting portion away from the opening, and the second elastic element can elastically press the limiting portion along a first direction and make the limiting portion slide in the sliding cavity along the first direction; When the limiting portion slides along the first direction, the hooking portion can approach or move away from the axis of the extended sleeve rod.

6. The socket wrench according to claim 1, characterized in that: A handle is fixedly provided on one end of the extended sleeve rod away from the sleeve head.

7. The socket wrench according to claim 1, characterized in that: The material of the sleeve head is beryllium bronze.

8. The socket wrench according to claim 6, characterized in that: A limit block is arranged at one end of the extended sleeve rod away from the handle, and a limit groove matching the limit block is arranged at a corresponding end of the sleeve head; When the limiting block is located in the limiting groove, the extended sleeve rod can drive the sleeve head to rotate synchronously around the axis of the extended sleeve rod.

9. The socket wrench according to claim 8, characterized in that: A through channel is provided on the side wall of the limit block, a third elastic element is provided in the through channel, third steel balls are provided on the outer sides of both ends of the third elastic element, the outer diameter of the third steel ball is smaller than the inner diameter of the through channel, and the outer diameter of the third steel ball is larger than the inner diameter of the end opening of the through channel; The third steel ball can protrude from the outer side wall of the limiting block; Accommodation grooves are respectively arranged on the inner side wall of the limiting groove corresponding to the positions of the third steel balls.

10. The socket wrench according to claim 1, characterized in that: The interior of the extended sleeve rod has a hollow cavity.

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