A structure optimized shaft under complex flow field conditions
Patent Information
- Application Number
- CN202522652378.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-15
- Publication Date
- 2026-09-22
- Estimated Expiration
- 2035-12-15
AI Technical Summary
[0004]针对现有技术的不足，本实用新型提供了一种复杂流场条件下结构优化轴，克服了现有技术的不足，设计合理，有效解决了复杂流场下分段长轴连接处易剪切断裂的问题
[0011]本实用新型提供了一种复杂流场条件下结构优化轴，具备以下有益效果：通过将连接螺纹改为英制惠氏螺纹并显著缩短内螺纹腔长度，直接增大了最薄弱环节的有效剪切面积。通过将轴段总数优化为三段，并将安装轴长度进行加长，大幅增加了传动系统的刚性基础段。这有效抑制了由“远端杠杆效应”引起的过大弯矩，使传递至连接处的载荷更为平缓，从源头降低了失效风险。方形变径柱与内螺纹腔的错位布置，既避免了传统设计导致的局部壁厚过薄，又利用其高刚度截面分担了径向剪切与弯曲载荷，使得轴在复杂流场下的整体最大变形量显著减小，变形分布更均匀。
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Figure CN224786160U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of biopharmaceutical equipment technology, specifically to a structurally optimized shaft under complex flow field conditions. Background Technology
[0002] In cell culture and fermentation processes in the biopharmaceutical field, large stirred reactors are one of the core pieces of equipment. Due to the physical limitations of the floor height in production workshops, the long shafts used to drive the impellers inside the reactor usually need to adopt a segmented design, that is, multiple shaft segments are assembled into the required overall length through connecting structures. During operation, such long shafts are subjected to complex flow field conditions composed of fluid turbulence, centrifugal force from impeller rotation, and asymmetric loads, and their connecting parts are subjected to continuous cyclic alternating stress and significant radial shear force.
[0003] Currently, the traditional segmented agitator shafts commonly used in this field rely on metric threads for connection between adjacent shaft segments. While this connection method satisfies basic assembly and torque transmission requirements to some extent, the stress in metric threaded connections tends to concentrate at the thread root under the repeated radial shear forces caused by complex flow fields. In particular, the internal threaded cavity within the connecting segment forms a localized weak area on the shaft cross-section. Numerous failure cases show that fractures often occur in this internal threaded cavity region, exhibiting typical shear fracture characteristics with a clean cross-section. This demonstrates that traditional threaded connections and cavity structures have failed to effectively address the problem of shear force transmission and dispersion. Furthermore, in existing technologies, for ease of machining and clamping, the square reducing column is typically placed directly on the outer wall of the shaft segment with the internal threaded cavity, meaning their axial positions are essentially corresponding or overlapping. This layout results in the shaft material being simultaneously weakened by the hollowing out of the internal threaded cavity and the cutting of the external square column on the same cross-section. The result is the formation of a circumferentially thinned "weak ring" in this region, significantly reducing its effective load-bearing cross-sectional area. On the one hand, the root of the internal thread itself is a stress concentration point; on the other hand, the corners of the square variable-diameter column introduce new stress concentrations. Under the action of complex flow field loads, the stress is highly superimposed and rapidly amplified in this extremely thin-walled region, making it very easy for fatigue cracks to initiate. Once a crack is formed, it will rapidly propagate on this weak cross-section, causing the shaft to undergo a clean shear fracture in the area where the internal thread cavity coincides with the square column. Utility Model Content
[0004] To address the shortcomings of existing technologies, this invention provides a structurally optimized shaft for complex flow field conditions. It overcomes the deficiencies of existing technologies, features a reasonable design, and effectively solves the problem of easy shear fracture at the connection points of segmented long shafts under complex flow field conditions. This significantly improves the fatigue strength, connection reliability, and operational stability of segmented stirring shafts under complex flow field conditions.
[0005] To achieve the above objectives, this utility model provides the following technical solution:
[0006] A shaft optimized for complex flow field conditions includes a mounting shaft and two shaft sections. The rear end of the mounting shaft is connected to the front end of one shaft section via a threaded connection structure. Adjacent shaft sections are also connected via threaded connections. The threaded connection structure comprises an external thread section and an internal thread cavity. The external thread section is located at the front end of the shaft section, and the internal thread cavity is located at the rear end of both the shaft section and the mounting shaft. The internal thread cavity and the external thread section are threaded together for a detachable connection. The external thread section and the internal thread cavity use a Whitworth thread structure. A first square reducing post is provided on the rear side of both the mounting shaft and the shaft section. The axial positions of the first square reducing post and the internal thread cavity are offset. A second square reducing post is provided at the front end of the shaft section near the external thread section.
[0007] Preferably, the length of the mounting shaft accounts for 30%-50% of the total shaft length.
[0008] Preferably, the mounting shaft and the surfaces of both shaft sections are provided with laser-printed traceability markings.
[0009] Preferably, the tightening direction of the internal thread cavity and the external thread section is consistent with the rotation direction of the structure-optimized shaft during operation.
[0010] Preferably, the mounting shaft and the outer surface of the shaft body are provided with at least one reinforcing rib at a position corresponding to the internal thread cavity.
[0011] This invention provides a structurally optimized shaft for complex flow field conditions, offering the following advantages: By changing the connecting thread to an Imperial Whitworth thread and significantly shortening the length of the internal thread cavity, the effective shear area of the weakest link is directly increased. By optimizing the total number of shaft segments to three and extending the installation shaft length, the rigid foundation section of the transmission system is significantly increased. This effectively suppresses excessive bending moments caused by the "far-end lever effect," making the load transmitted to the connection point more gradual and reducing the risk of failure from the source. The staggered arrangement of the square variable-diameter column and the internal thread cavity avoids the localized excessive wall thickness caused by traditional designs and utilizes its high-rigidity section to share radial shear and bending loads, resulting in a significant reduction in the overall maximum deformation of the shaft under complex flow field conditions and a more uniform deformation distribution. Attached Figure Description
[0012] To more clearly illustrate the technical solutions in this utility model or the prior art, the accompanying drawings used in the description of this utility model or the prior art will be briefly introduced below.
[0013] Figure 1 This is a schematic diagram of the structure of this utility model;
[0014] Figure 2 This is a schematic diagram of the cross-sectional structure of this utility model;
[0015] Figure 3 This is a schematic diagram of the cross-sectional structure of the threaded connection structure in this utility model;
[0016] Figure 4 This is a schematic diagram of the structure when the two shaft sections are separated in this utility model;
[0017] Figure 5 for Figure 4 A magnified view of a section at point A in the middle;
[0018] Explanation of the labels in the diagram:
[0019] 1. Mounting shaft; 2. Shaft body; 3. Threaded connection structure; 4. First square reducing post; 5. Second square reducing post; 31. External thread section; 32. Internal thread cavity. Detailed Implementation
[0020] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings.
[0021] Example 1, as Figures 1 to 5 As shown, a shaft with optimized structure under complex flow field conditions includes a mounting shaft 1 and two shaft sections 2. The rear end of the mounting shaft 1 is connected to the front end of one of the shaft sections 2 via a threaded connection structure 3. Adjacent shaft sections 2 are also connected to each other via threaded connection structures 3. The threaded connection structure 3 includes an external thread section 31 and an internal thread cavity 32. The external thread section 31 is located at the front end of the shaft section 2, and the internal thread cavity 32 is located at the rear end of both the shaft section 2 and the mounting shaft 1. The internal thread cavity 32 and the external thread section 31 are threaded together to achieve a detachable connection. The external thread section 31 and the internal thread cavity 32 adopt an Imperial Whitworth thread structure. A first square reducing post 4 is provided on the rear side of both the mounting shaft 1 and the rear side of the shaft section 2. The axial positions of the first square reducing post 4 and the internal thread cavity 32 are offset from each other. A second square reducing post 5 is provided at the front end of the shaft section 2 near the external thread section 31.
[0022] Working principle:
[0023] When the optimized shaft rotates in the complex flow field within the reactor, it primarily bears the following combined loads: the torque (torsional) driven by the motor, the axial thrust generated by the fluid resistance on the blades, and the radial (bending) and shear loads caused by fluid turbulence and the centrifugal force of the blades. In traditional shaft structures, these loads are ultimately concentrated and transmitted through the threaded connection pair, forming stress peaks in its hollow section. This invention optimizes the total number of shaft segments to three, including one mounting shaft 1 and two shaft body segments 2, and extends the length of the mounting shaft 1 to effectively shorten the force transmission path from the far end of the load (blade) to the fixed end (reducer), thereby reducing the overall shaft's tendency to flexural deformation.
[0024] Furthermore, in this embodiment, the threaded connection structure 3 uses a British Standard Whitworth thread with a 55° tooth angle and a rounded root instead of a traditional metric thread. The rounded root of the British Standard Whitworth thread allows for a smoother stress transition, and its thread pair exhibits better self-alignment and anti-loosening capabilities under the same preload. Moreover, in this embodiment, based on the stress distribution characteristics of the British Standard Whitworth thread, the axial length of the internal thread cavity 32 can be shortened, thereby reducing the axial dimension of the weakest cavity section in the connection area, increasing the effective shear area of the material at that location, and thus effectively improving the shear strength.
[0025] In addition, by setting the first square reducing column 4 on the rear side of the shaft and distributing it separately from the internal thread cavity 32, the problem of excessively thin wall thickness caused by the superposition of "internal cavity hollowing" and "external square cutting" in the same cross section in the traditional design is effectively avoided, ensuring the integrity of the wall thickness of the threaded connection area body.
[0026] In Example 2, as a further preferred embodiment of Example 1, the length of the mounting shaft 1 accounts for 30%-50% of the total shaft length. By extending the length of the mounting shaft 1 to 30%-50% of the total shaft length, the proportion of rigid sections in the entire transmission chain can be significantly increased. This allows the bending moment and shear force transmitted from the distal blades to be more effectively absorbed and attenuated in the longer rigid sections before being transmitted to subsequent connections. This significantly reduces the peak stress on subsequent connection structures from the load source. The lower limit of 30% ensures that the mounting shaft has sufficient length to provide the aforementioned rigid foundation and protective effect. The upper limit of 50% takes into account the actual workshop height limitations and equipment installability. An excessively long mounting shaft 1 would encroach on the arrangement space of subsequent shaft sections and blades, potentially failing to meet the insertion depth requirements of reactors with specific volumes. The 50% upper limit ensures that maximum rigidity benefits are achieved without sacrificing the equipment's versatility and assemblability.
[0027] In Example 3, as a further preferred embodiment of Example 1, laser-printed traceability markings are provided on the surfaces of the mounting shaft 1 and the two shaft segments 2. By assigning a permanent and unique traceability marking to each mounting shaft 1 and each shaft segment 2, and by associating this marking with equipment operation records (such as production batch records), the cumulative actual operating time or stirring cycle of each shaft segment can be accurately measured. This ensures that when reassembling after disassembly, cleaning, and maintenance, each component can be accurately placed, and the assembled components are within a compatible service life. This avoids problems such as uneven stress and mismatched connections caused by mixing components.
[0028] In Example 4, as a further preferred embodiment of Example 1, the tightening direction of the internal thread cavity 32 and the external thread section 31 is consistent with the rotation direction of the optimized shaft during operation. By setting the tightening direction to be consistent with the working rotation direction, when the main working torque transmitted by the drive end of the stirring shaft acts on the threaded pair during normal operation, an additional torque component is generated to further tighten the threads. This ensures that the connection structure will not loosen during dynamic operation; in fact, its preload may be maintained or even slightly enhanced under working load. Thus, the harmful working load that could lead to loosening is transformed into a beneficial active force that maintains the connection. In addition, the British standard Whitworth thread itself has better stress distribution and a certain self-centering ability under load. When the working torque is converted into tightening force, this optimized thread profile can more evenly transmit the force to the entire meshing surface, avoiding local failure caused by excessive stress concentration, making the "tightening with each turn" effect smoother and more reliable. Furthermore, in biopharmaceutical applications, micro-movements at the connection may cause media to seep into the thread gaps, leading to corrosion or contamination. The self-tightening effect of consistent rotation can dynamically compensate for minute gaps that may be caused by vibration or temperature changes, helping to maintain a tight fit at the connection interface and improving the overall sealing and cleanliness of the equipment.
[0029] In Example 4, as a further preferred embodiment of Example 1, at least one reinforcing rib is provided on the outer surface of the mounting shaft 1 and shaft body 2 at a position corresponding to the internal thread cavity 32. By adding a reinforcing rib on the outer surface corresponding to the axial direction of the internal thread cavity, the originally weakest annular region is locally reinforced, significantly improving its resistance to radial shear force and bending stress, fundamentally suppressing the tendency for cracks to initiate at the root of the thread cavity. When the load is transferred to the internal thread cavity region, the presence of the reinforcing rib changes the local stiffness distribution. A portion of the stress is guided to the stiffer reinforcing rib, achieving active stress diversion and redistribution. This allows the stress flow line to transition more smoothly, effectively reducing the stress concentration factor at that location, thereby significantly improving the fatigue life of that region.
[0030] This invention directly increases the effective shear area of the weakest link by changing the connecting thread to an Imperial Whitworth thread and significantly shortening the length of the internal thread cavity. By optimizing the total number of shaft segments to three and extending the length of the mounting shaft, the rigid foundation section of the transmission system is significantly increased. This effectively suppresses excessive bending moments caused by the "far-end lever effect," making the load transmitted to the connection point more gradual and reducing the risk of failure from the source. The staggered arrangement of the square variable-diameter column and the internal thread cavity avoids the localized excessive wall thickness caused by traditional designs and utilizes its high-rigidity section to distribute radial shear and bending loads, resulting in a significant reduction in the overall maximum deformation of the shaft under complex flow fields and a more uniform deformation distribution.
[0031] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.
Claims
1. A structurally optimized shaft under complex flow field conditions, comprising a mounting shaft (1) and two shaft sections (2), wherein the rear end of the mounting shaft (1) is connected to the front end of one shaft section (2) via a threaded connection structure (3), and adjacent shaft sections (2) are connected to each other via a threaded connection structure (3), characterized in that: The threaded connection structure (3) includes an external thread section (31) and an internal thread cavity (32). The external thread section (31) is located at the front end of the shaft (2), and the internal thread cavity (32) is located at the rear end of the shaft (2) and the rear end of the mounting shaft (1). The internal thread cavity (32) and the external thread section (31) are threaded together to achieve a detachable connection. The external thread section (31) and the internal thread cavity (32) adopt the British Whitworth thread structure. The rear side of the mounting shaft (1) and the rear side of the shaft (2) are both provided with a first square reducing post (4). The axial position of the first square reducing post (4) and the internal thread cavity (32) is staggered. The front end of the shaft (2) is provided with a second square reducing post (5) near the external thread section (31).
2. The structural optimization shaft under complex flow field conditions according to claim 1, characterized in that: The length of the mounting shaft (1) accounts for 30%-50% of the total shaft length.
3. The structural optimization shaft under complex flow field conditions according to claim 1, characterized in that: The mounting shaft (1) and the two shaft sections (2) are all equipped with laser-printed traceability markings.
4. The structural optimization shaft under complex flow field conditions according to claim 1, characterized in that: The internal thread cavity (32) and the external thread section (31) are tightened in the same direction as the rotation direction of the structure optimization shaft during operation.
5. The structural optimization shaft under complex flow field conditions according to claim 1, characterized in that: At least one reinforcing rib is provided at the position corresponding to the inner thread cavity (32) on the outer surface of the mounting shaft (1) and the shaft body (2).