Tail shaft structure of spiral conveyor
By introducing a positioning groove and a clearance fit of a precision-machined stepped ring into the tail shaft structure of the screw conveyor, combined with improvements to the wear-resistant sleeve and support structure, the problems of insufficient concentricity and easy wear in the traditional tail shaft structure have been solved. This has achieved efficient concentricity control and wear resistance, simplified the maintenance process, and improved the operational stability and lifespan of the equipment.
Patent Information
- Application Number
- CN202520673963.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-10
- Publication Date
- 2026-02-27
- Estimated Expiration
- 2035-04-10
AI Technical Summary
Traditional screw conveyor tail shafts suffer from insufficient concentricity control, are prone to wear, are complex to maintain, have high processing costs, and are difficult to disassemble.
The design employs a positioning groove and tail shaft clearance fit, combined with a precision-machined stepped ring and wear-resistant sleeve design. Concentricity is ensured through radial and axial positioning, and Teflon sleeves are used to reduce wear. The support structure enhances stability through bent shell and feet.
It improves concentricity control and wear resistance, simplifies maintenance procedures, reduces costs, extends equipment lifespan, and enhances operational stability and overall performance.
Smart Images
Figure CN223950077U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to material conveying equipment technical field especially relates to a spiral conveyor tail shaft structure. BACKGROUND
[0002] As the key equipment of material continuous conveying, spiral conveyors are widely used in the fields of mining, chemical industry, grain processing, etc. The core component of the spiral conveyor, the spiral conveying shaft, advances the material by rotating and pushing, while the tail shaft structure, as the key part of support and positioning, directly affects the running stability and service life of the conveyor. In the traditional design, the optimization of the spiral conveyor is mostly focused on the main shaft structure, and the tail shaft structure is often ignored, resulting in problems such as insufficient control of concentricity, easy wear, and complex maintenance.
[0003] The existing tail shaft structure usually ensures the concentricity with the main shaft by precisely machining the inner hole of the tail flange, but such machining process is complex and costly, and the flange and the tail shaft are mostly fixedly connected, which is difficult to disassemble and maintain. In addition, the wear resistance of the tail shaft and the spiral conveying shaft is insufficient, and the gap will increase due to wear after long-term operation, further aggravating the concentricity deviation and causing vibration and even equipment failure. Although rigid welding rib plates are used to enhance the structure in some designs, there are still defects such as stress concentration and easy deformation.
[0004] In view of the above problems, the existing technology needs to be improved. SUMMARY
[0005] In order to solve the above problems, the purpose of the utility model is to provide a spiral conveyor tail shaft structure, which has the advantages of improving the control of concentricity, enhancing the wear resistance, and simplifying the maintenance process.
[0006] In order to achieve the above purpose, the utility model adopts the following technical scheme:
[0007] The present application provides a spiral conveyor tail shaft structure, and the technical scheme is as follows: a rack, a spiral conveying shaft rotatingly arranged in the shell of the rack, and a driving assembly connected with the input end of the spiral conveying shaft; a positioning groove is formed on the tail end of the spiral conveying shaft, a tail shaft is formed on the inner wall of the shell of the rack and is arranged concentrically with the spiral conveying shaft, and the tail shaft is inserted into the positioning groove and is gap-fitted with the positioning groove.
[0008] Further, the present application further provides that a tail flange is arranged on the end of the shell, a precision machining stepped ring is fixedly connected in the inner hole of the tail flange, and the tail shaft is fixedly connected on the precision machining stepped ring.
[0009] Further, the present application further provides that a radial convex ring is protrudingly arranged on the edge of the ring body of the precision machining stepped ring in a radial direction, and the radial convex ring is arranged and fixed in the inner hole of the tail flange, so as to ensure the concentricity through radial positioning.
[0010] Further, the application also provides that the edge of the ring body of the finishing stepped ring is provided with an axial convex ring protruding axially outward, and an annular groove is formed in the axial convex ring; a threaded hole is constructed on the ring body in the axial convex ring; an end plate is fixedly connected to the outer end of the tail shaft, and a through hole is arranged on the edge of the end plate; when the tail shaft is installed on the finishing stepped ring, the end plate is embedded in the annular groove, the through hole is aligned with the threaded hole and connected through a screwing component, and axial fixation is achieved.
[0011] Further, the application also provides that the spiral conveying shaft comprises a hollow shaft and spiral blades arranged on the hollow shaft; a tail end chamber is formed in the tail end of the hollow shaft through a thrust plate, an inner steel sleeve is fixedly connected in the tail end chamber, and a wear-resistant sleeve is fixedly connected in the inner steel sleeve; the positioning groove is formed in the wear-resistant sleeve, and the tail shaft is inserted into the positioning groove of the wear-resistant sleeve.
[0012] Further, the application also provides that a circular ring rib plate is arranged between the inner wall of the tail end chamber and the outer wall of the inner steel sleeve, and the inner and outer sides of the circular ring rib plate are respectively welded and fixed with the outer wall of the inner steel sleeve and the inner wall of the tail end chamber, so as to enhance the structural rigidity.
[0013] Further, the application also provides that the rack further comprises a support leg supporting the shell, and the shell is a bent shell. Further, the application also provides that the wear-resistant sleeve is a Teflon sleeve.
[0014] As can be seen from the above, the spiral conveyor tail shaft structure provided by the application effectively improves the concentricity control, enhances the wear resistance, and simplifies the maintenance process by constructing the positioning groove and the gap fit of the tail shaft, and designing the finishing stepped ring and the wear-resistant sleeve, and has the advantages of improving the equipment operation stability and service life. BRIEF DESCRIPTION OF DRAWINGS
[0015] Figure 1 FIG. 1 is a structural schematic diagram of a spiral conveyor provided by the application.
[0016] Figure 2 FIG. 4 is an enlarged view of part A of FIG. 1. Figure 1
[0017] Figure 3 FIG. 6 is a schematic diagram of a finishing stepped ring provided by the application.
[0018] Figure 4 FIG. 7 is a schematic diagram of a finishing stepped ring provided by the application. DETAILED DESCRIPTION
[0019] The embodiments of the present application are described below in detail, examples of which are shown in the drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the drawings are exemplary, and are intended to explain the present application, and cannot be understood as a limitation of the present application.
[0020] In the description of the present application, it is to be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "clockwise", "counterclockwise" and the like are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.
[0021] In addition, the terms "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise stated, the meaning of "a plurality of" is two or more, unless otherwise explicitly limited.
[0022] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.
[0023] In the present application, unless otherwise explicitly specified and limited, the first feature "above" or "below" the second feature can include the first and second features directly contacting, or the first and second features not directly contacting but contacting through another feature between them. Moreover, the first feature "above", "above" and "above" the second feature includes the first feature directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" the second feature includes the first feature directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.
[0024] As Figures 1-4As shown, the application proposes a spiral conveyor tail shaft structure, which includes a rack 9, a spiral conveying shaft rotatingly arranged in a shell 8 of the rack 9, and a driving assembly connected with an input end of the spiral conveying shaft; a positioning groove 15 is constructed on a tail end of the spiral conveying shaft, and a tail shaft 5 is constructed on an inner wall of the shell 8 of the rack 9 and is concentrically arranged with the spiral conveying shaft, the tail shaft 5 is inserted into the positioning groove 15 and is gap-fitted with the positioning groove 15.
[0025] The gap-fitting of the tail shaft 5 and the positioning groove 15 can achieve different fitting accuracies by adjusting the gap size, and the gap size is usually controlled between 0.1mm and 0.5mm to ensure that the tail shaft 5 can be smoothly inserted and the concentricity is maintained. The materials of the rack 9 and the shell 8 can be selected as high-strength steel or aluminum alloy to enhance the stability and durability of the structure. The driving assembly can adopt a motor, a hydraulic motor or other power sources to provide the rotating power required by the spiral conveying shaft. In addition, the construction of the positioning groove 15 can be realized by machining or casting process to ensure the dimensional accuracy and surface finish. The concentric arrangement of the tail shaft 5 can be realized by precise machining or assembly process to ensure that the axis of the tail shaft 5 coincides with that of the spiral conveying shaft. The connection of the driving assembly can adopt a shaft coupling, a gear or other transmission device to ensure the stability and efficiency of power transmission.
[0026] The technical scheme realizes the concentric arrangement of the tail shaft 5 and the spiral conveying shaft by constructing the positioning groove 15 and the tail shaft 5 and ensuring the gap-fitting of the tail shaft 5 and the positioning groove 15. The design of the rack 9 and the shell 8 provides a stable support structure, and the driving assembly ensures the rotating power of the spiral conveying shaft. The fitting of the positioning groove 15 and the tail shaft 5 not only simplifies the installation and maintenance process, but also improves the accuracy of the concentricity control and reduces the problem of gap increase caused by wear, thereby enhancing the operation stability and service life of the equipment. Compared with the prior art, the technical scheme optimizes the tail shaft structure, solves the technical problems of insufficient concentricity control, easy wear and complex maintenance, and has high practicability and innovation.
[0027] Further, the application also proposes that a tail flange 7 is arranged on an end portion of the shell 8, a finish machining stepped ring 4 is fixedly connected in an inner hole of the tail flange 7, and the tail shaft 5 is fixedly connected on the finish machining stepped ring 4. Thus, the tail shaft 5 can be accurately fixed on the finish machining stepped ring 4 through the finish machining stepped ring 4 fixedly connected in the inner hole of the tail flange 7, thereby ensuring the concentricity of the tail shaft 5 and the tail flange 7. The machining accuracy and fixing mode of the finish machining stepped ring 4 directly affect the positioning accuracy of the tail shaft 5, thereby ensuring the operation stability and service life of the spiral conveyor. In contrast, in the traditional structure, the tail flange 7 needs to be finished machined to ensure the concentricity of the tail shaft 5, which has a large machining cost and cannot be disassembled. The tail shaft 5 structure in the present scheme not only can be batch finished machined, but also is convenient for maintenance and disassembly, saving time and effort.
[0028] As shown in Figure 4 The radially outward protruding edge of the ring body of the finishing stepped ring 4 is provided with a radial protruding ring 16, which is erected and fixed in the inner hole of the tail flange 7 to ensure concentricity through radial positioning. Specifically, the radial protruding ring 16 is arranged so that the finishing stepped ring 4 can be tightly fitted with the inner hole of the tail flange 7. The protruding part of the radial protruding ring 16 is formed by machining or casting process, which is matched in size and shape with the inner hole of the tail flange 7, ensuring that the two can be accurately aligned when assembled. The fixing method of the radial protruding ring 16 is generally integrated, and can also include welding, bolt connection or interference fit, etc., the specific choice depends on the actual application scenario and material properties.
[0029] For this, the technical scheme effectively solves the problems of complex machining process, high cost and difficult disassembly and maintenance in traditional design through radial positioning. The arrangement of the radial protruding ring 16 not only simplifies the assembly process, but also improves the stability and service life of the structure. Compared with the prior art, this scheme does not need to process the inner hole of the tail flange 7 with high precision, which reduces the manufacturing cost, and at the same time ensures the concentricity of the finishing stepped ring 4 and the tail flange 7 through radial positioning, reduces the vibration and wear during operation, and improves the reliability and maintenance convenience of the equipment.
[0030] Further, the axially outward protruding edge of the ring body of the finishing stepped ring 4 is provided with an axial protruding ring 13, and an annular groove is formed in the axial protruding ring 13; a threaded hole is constructed on the ring body in the axial protruding ring 13; an end plate 14 is fixed on the outer end of the tail shaft 5, and a through hole is arranged on the edge of the end plate 14; when the tail shaft 5 is installed on the finishing stepped ring 4, the end plate 14 is embedded in the annular groove, the through hole is aligned with the threaded hole and connected through a screwing component, realizing axial fixation. Specifically, the design of the axial protruding ring 13 makes the connection between the finishing stepped ring 4 and the tail shaft 5 more stable, and the introduction of the annular groove provides accurate positioning space for the embedding of the end plate 14, thereby ensuring the concentricity between the tail shaft 5 and the finishing stepped ring 4. The threaded hole is arranged corresponding to the through hole on the end plate 14, and the axial fixation of the tail shaft 5 is realized through the connection of the screwing component. This structural design not only simplifies the installation process, but also improves the stability and concentricity of the tail shaft 5 during operation. As a preferred embodiment, the screwing component can adopt a bolt or a screw, and the material thereof should be selected as high-strength alloy steel to ensure the reliability and durability of the connection. In addition, the thickness and material of the end plate 14 also need to be optimized according to the actual working condition to withstand the axial force and vibration during operation.
[0031] Thus, the technical scheme realizes the axial fixation between the tail shaft 5 and the finishing stepped ring 4 through the connection of the screwing components by the axial protruding ring 13 and the annular groove design of the finishing stepped ring 4 and the cooperation of the through hole and the screw hole on the end plate 14 of the tail shaft 5. The structure design not only simplifies the installation process, but also improves the stability and concentricity of the tail shaft 5 in operation, effectively solving the problem of loose axial fixation of the tail shaft 5 in the traditional design. Compared with the prior art, the scheme has the advantages of simple structure, convenient installation, stable operation and the like, and significantly improves the overall performance and service life of the screw conveyor.
[0032] As shown in Figure 1 , the screw conveying shaft includes a hollow shaft 10 and a spiral blade 11 arranged on the hollow shaft 10; the tail end inside the hollow shaft 10 is formed with a tail end chamber 12 through a thrust plate 1, an inner steel sleeve 2 is fixed in the tail end chamber 12, and a wear-resistant sleeve 6 is fixed in the inner steel sleeve 2; a positioning groove 15 is formed in the wear-resistant sleeve 6, and a tail shaft 5 is inserted into the positioning groove 15 of the wear-resistant sleeve 6. Specifically, the hollow shaft 10 and the spiral blade 11 constitute the main structure of the screw conveying shaft, and the material is pushed forward by rotation. The thrust plate 1 forms the tail end chamber 12 at the tail end of the hollow shaft 10, the inner steel sleeve 2 is fixed in the tail end chamber 12, the wear-resistant sleeve 6 is fixed in the inner steel sleeve 2, the positioning groove 15 is formed in the wear-resistant sleeve 6, and the tail shaft 5 is inserted into the positioning groove 15 of the wear-resistant sleeve 6. This structure ensures the concentricity of the tail shaft 5 and the screw conveying shaft through the insertion cooperation of the positioning groove 15 of the wear-resistant sleeve 6 and the tail shaft 5, reduces wear and tear, prolongs the service life, and facilitates disassembly and maintenance.
[0033] Compared with the prior art, the technical scheme effectively solves the technical problems of insufficient concentricity control, easy wear and tear and complex maintenance of the tail shaft structure of the screw conveyor through the insertion cooperation of the positioning groove 15 of the wear-resistant sleeve 6 and the tail shaft 5. The use of the wear-resistant sleeve 6 reduces the direct friction between the tail shaft 5 and the screw conveying shaft, prolongs the service life of the equipment. At the same time, the design of the positioning groove 15 makes the installation and disassembly of the tail shaft 5 more convenient, and reduces the maintenance cost. In addition, the setting of the inner steel sleeve 2 and the thrust plate 1 enhances the rigidity of the structure, and further improves the operation stability of the equipment.
[0034] Further, a circular ring rib plate 3 is arranged between the inner wall of the tail end chamber 12 and the outer wall of the inner steel sleeve 2, and the inner and outer sides of the circular ring rib plate 3 are respectively welded and fixed with the outer wall of the inner steel sleeve 2 and the inner wall of the tail end chamber 12 to enhance the structural rigidity. Specifically, the circular ring rib plate 3 is an annular structure, and its inner side is welded and fixed with the outer wall of the inner steel sleeve 2, and its outer side is welded and fixed with the inner wall of the tail end chamber 12. The thickness and width of the circular ring rib plate 3 can be adjusted according to actual needs to ensure that it can effectively share and transfer stress. The material of the circular ring rib plate 3 can be the same steel as the inner steel sleeve 2 and the tail end chamber 12 to ensure the firmness of the welding and the stability of the overall structure. In addition, the welding method of the circular ring rib plate 3 can adopt continuous welding or intermittent welding, and the specific choice depends on the stress condition and process requirement of the structure. Through the arrangement and welding of the circular ring rib plate 3, the structural rigidity between the tail end chamber 12 and the inner steel sleeve 2 is significantly enhanced. The circular ring rib plate 3 not only shares the stress between the inner steel sleeve 2 and the tail end chamber 12, but also ensures the integrity and stability of the structure through welding. Compared with the prior art, this technical solution effectively solves the problem of unstable structure caused by stress concentration and easy deformation in traditional design. The welding of the circular ring rib plate 3 not only improves the overall strength of the structure, but also ensures the concentricity between the tail shaft 5 and the spiral conveying shaft, thereby improving the running stability and service life of the equipment.
[0035] Further, the wear-resistant sleeve 6 is a Teflon sleeve. The Teflon sleeve has excellent wear resistance and self-lubricating property, which can effectively reduce the wear of the matching part of the tail shaft 5 and the spiral conveying shaft, prolong the service life of the equipment, and reduce the maintenance cost. Through this technical feature, the tail shaft 5 structure can maintain stable concentricity during long-term operation, reducing the increase of gap and equipment failure caused by wear. The Teflon sleeve can be realized in various ways, for example, the Teflon material can be directly molded into the wear-resistant sleeve 6 by injection molding process, or the Teflon material can be pressed into shape by hot pressing process. In addition, the thickness of the Teflon sleeve can be adjusted according to the actual working condition to ensure its wear resistance and service life. As a preferred embodiment, the inner surface of the Teflon sleeve can be further polished to reduce the friction coefficient and improve the self-lubricating effect.
[0036] Specifically, the application of the Teflon sleeve solves the problem of insufficient wear resistance in the traditional tail shaft 5 structure. The Teflon material has low friction coefficient and high wear resistance, which can form a self-lubricating film at the matching part of the tail shaft 5 and the spiral conveying shaft, reducing direct contact and friction, thereby effectively reducing wear. Compared with the prior art, the Teflon sleeve not only improves the wear resistance of the tail shaft 5 structure, but also simplifies the maintenance process and reduces the equipment failure and downtime caused by wear. Therefore, the tail shaft 5 structure can maintain stable concentricity during long-term operation, improving the overall operation efficiency and reliability of the spiral conveyor.
[0037] In addition, as shown in Figure 1 The rack 9 also includes supporting legs to support the shell 8, which is a bent shell. The design of the supporting legs significantly improves the stability of the shell 8 by increasing the support points, reducing the risk of deformation caused by vibration or external force. The bent design of the shell 8 not only simplifies the structure, but also improves the overall rigidity and anti-deformation ability, effectively solving the technical problems of complex structure and insufficient stability of the rack 9 supporting the shell 8. Specifically, the supporting legs can be implemented in various forms, such as fixed supporting legs or adjustable supporting legs. The fixed supporting legs are fixed on the rack 9 by welding or bolt connection, suitable for scenarios with high stability requirements. The adjustable supporting legs can adjust the height through threads or hydraulic mechanisms, facilitating fine tuning under different installation conditions to ensure the levelness and stability of the shell 8. In addition, the design of the bent shell 8 can adopt single bending or multiple bending processes, and the specific bending angle and shape can be adjusted according to actual needs to optimize the structural strength and space utilization.
[0038] Therefore, the technical scheme of the present application combines the supporting legs and the bent shell 8, not only simplifying the structure of the rack 9 supporting the shell 8, but also significantly improving its stability and rigidity. Compared with the prior art, this scheme avoids complex processing techniques and high costs, while through the multi-point support of the supporting legs and the structural optimization of the bent shell 8, effectively reducing vibration and deformation, prolonging the service life of the equipment, and reducing maintenance costs.
[0039] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.
[0040] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and cannot be construed as limiting the present application. Those skilled in the art can make changes, modifications, replacements and variations to the above embodiments without departing from the principles and purposes of the present application within the scope of the present application.
Claims
1. A screw conveyor tail shaft structure, comprising a frame (9), a screw conveying shaft rotatably arranged in a housing (8) of the frame (9), and a driving assembly connected to an input end of the screw conveying shaft; characterized in that: a positioning groove (15) is formed on a tail end of the screw conveying shaft, a tail shaft (5) concentrically arranged with the screw conveying shaft is formed on an inner wall of the housing (8) of the frame (9), the tail shaft (5) is inserted into the positioning groove (15) and is in clearance fit with the positioning groove (15).
2. The screw conveyor tail shaft structure according to claim 1, characterized in that: a tail flange (7) is arranged on an end of the housing (8), a finished stepped ring (4) is fixedly connected in a bore of the tail flange (7), and the tail shaft (5) is fixedly connected to the finished stepped ring (4).
3. The screw conveyor tail shaft structure according to claim 2, characterized in that: a radial protruding ring (16) is arranged on a radially outward protruding edge of the finished stepped ring (4), and the radial protruding ring is arranged and fixed in the bore of the tail flange (7) to ensure concentricity through radial positioning.
4. The screw conveyor tail shaft structure according to claim 3, characterized in that: an axial protruding ring (13) is arranged on an axially outward protruding edge of the finished stepped ring (4), and an annular groove is formed in the axial protruding ring (13); screw holes are formed on a ring body in the axial protruding ring (13); an end plate (14) is fixedly connected to an outer end of the tail shaft (5), and a through hole is arranged on an edge of the end plate (14); when the tail shaft (5) is mounted on the finished stepped ring (4), the end plate (14) is embedded in the annular groove, the through hole is aligned with the screw hole, and the tail shaft (5) is connected through a screwing part to realize axial fixation.
5. The screw conveyor tail shaft structure according to claim 1, characterized in that: the screw conveying shaft comprises a hollow shaft (10) and a screw blade (11) arranged on the hollow shaft (10); a tail end cavity (12) is formed in a tail end of the hollow shaft (10) through a thrust plate (1), an inner steel sleeve (2) is fixedly connected in the tail end cavity (12), and a wear-resistant sleeve (6) is fixedly connected in the inner steel sleeve (2); the positioning groove (15) is formed in the wear-resistant sleeve (6), and the tail shaft (5) is inserted into the positioning groove (15) of the wear-resistant sleeve (6).
6. The screw conveyor tail shaft structure according to claim 5, characterized in that: a circular ring rib plate (3) is arranged between an inner wall of the tail end cavity (12) and an outer wall of the inner steel sleeve (2), and the circular ring rib plate (3) is welded and fixed to the outer wall of the inner steel sleeve (2) and the inner wall of the tail end cavity (12) respectively to enhance structural rigidity.
7. The screw conveyor tail shaft structure according to claim 1, characterized in that: the frame (9) further comprises a supporting leg supporting the housing (8), and the housing (8) is a bent housing.
8. The screw conveyor tail shaft structure according to claim 5, characterized in that: the wear-resistant sleeve (6) is a Teflon sleeve.