Integrated clutch connecting device for bicycle transmission system

Abstract

The invention provides an integrated clutch connecting device for a bicycle transmission system. The integrated clutch connecting device comprises a hub. The hub body comprises two end parts which are symmetrically arranged, the outer wall of each end part is provided with an inclined boss which is arranged in a surrounding manner, one end part is connected with a tower footing, the inner wall of the tower footing is provided with an inner boss and continuous annular ratchets, a shaft core is arranged in the tower footing in a penetrating manner, the other end of the tower footing is provided with a second gasket, and the other end of the tower footing is provided with a first gasket; and the spokes are connected between the hub and the hub body. The transmission system has excellent buffering performance, reliable power transmission and compact structural layout due to the unique combination design, and meanwhile, the performance of the transmission system is comprehensively improved through the collaborative design of the innovative double-flat-wire spring interlocking structure and the integrated ratchet wheel.

Description

Technical Field

[0001] The invention relates to an integrated clutch connection device for a bicycle transmission system. Background Art

[0002] In a bicycle transmission system, the hub's clutch connection is a core component for unidirectional power transmission. Its performance directly impacts power transmission efficiency, responsiveness, and long-term reliability. Traditional clutch connections typically utilize a separate ratchet wheel and an independent compression spring. The pawl engages the ratchet wheel under the preload of the spring, achieving unidirectional drive. While this structure is technically mature and widely used, it still faces the following key challenges in practical use:

[0003] Large power transmission loss: Traditional clutch devices rely on a coil spring to push the pawl into engagement with the ratchet. However, due to the limited spring preload, the pawl has a certain amount of idle travel (approximately 0.5° to 1.5°) during the initial engagement phase, resulting in an inability to immediately transmit pedaling force and causing power loss. Especially when the torque is high (such as when climbing a slope or accelerating), the spring compression increases, and the contact pressure between the pawl and ratchet teeth is unevenly distributed. Torque loss can reach 8% to 15%, seriously affecting transmission efficiency.

[0004] Decreased engagement stability after long-term use: Traditional compression springs are prone to plastic deformation or fatigue degradation under prolonged stress, resulting in reduced rebound force. After riding for more than 5,000 kilometers, the spring rebound force may decrease by 20% to 30%, resulting in insufficient engagement depth between the pawl and the ratchet wheel, or even slipping, affecting riding safety and reliability.

[0005] Based on this, the present invention proposes an innovative design of a double flat wire spring interlocking structure + an integrated ratchet, aiming to fundamentally solve the inherent defects of traditional clutch devices and achieve more efficient and reliable power transmission. Summary of the Invention

[0006] The present invention provides an integrated clutch connection device for a bicycle transmission system, which can effectively solve the above problems.

[0007] The present invention is achieved in that:

[0008] An integrated clutch connection device for a bicycle transmission system, comprising

[0009] wheel hub;

[0010] The hub body comprises two symmetrically arranged ends, the outer wall of each end being provided with a surrounding inclined boss, one of the ends being connected to a freewheel base, the inner wall of the freewheel base being provided with an inner boss and a continuous annular ratchet, an axle core being passed through the inner wall, the other end being provided with a second liner, and the other end being provided with a first liner;

[0011] Spokes, connected between the hub and the hub body;

[0012] A ratchet assembly, integrally meshed with the freehub body, comprising: an integral ratchet ring, elastically connected to the inner wall of the freehub body through a customized spring system;

[0013] The customized spring system is composed of two identical flat wire compression springs a and flat wire compression springs b which are spirally tightened with each other, forming a cross-sectional shape of a disc spring group. Among them,

[0014] The spiral directions of the two flat wire compression springs a and flat wire compression springs b are opposite;

[0015] After being tightened with each other, a composite spring module with non-linear stiffness characteristics is formed;

[0016] The inner convex platform dynamically cooperates with the composite spring module, so that the meshing force of the integral ratchet ring is automatically adjusted according to the load.

[0017] The beneficial effects of the present invention are:

[0018] (1) Through the collaborative design of the innovative double flat wire spring interlocking structure and the integral ratchet, the present invention realizes a comprehensive improvement in the performance of the transmission system - the double springs that are spirally tightened with each other generate a progressive stiffness change during the compression process, enabling the ratchet meshing force to be automatically adjusted according to the riding load, providing a compliant buffer under low load and a firm support under high load; at the same time, the integral ratchet structure converts the partial meshing of the traditional split design into a full-circumference uniform force, not only effectively eliminating the wear problem of the ratchet mechanism, but also significantly reducing the operating noise; this unique combined design enables the transmission system to have excellent buffer performance, reliable power transmission and a compact structural layout. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 is the front view of the present invention.

[0021] Figure 2 is the connection schematic diagram of the spoke and the end part of the present invention.

[0022] Figure 3 is the structural schematic diagram of the hub body of the present invention.

[0023] Figure 4 It is a schematic diagram showing the unfolded structure of the hub body of the present invention.

[0024] Figure 5 It is a schematic diagram showing the structure of the top cover and the bottom cover of the present invention.

[0025] Figure 6 It is a schematic diagram showing the unfolded structure of the top cover and the bottom cover of the present invention.

[0026] Figure 7 It is a schematic diagram showing the flat wire compression spring a and the flat wire compression spring b of the present invention.

[0027] Figure 8 It is a schematic diagram showing the structure of the first ratchet ring of the present invention.

[0028] Figure 9 It is an assembly schematic diagram of the freehub body, the axle core, the top cover, the bottom cover, the flat wire compression spring a and the flat wire compression spring b of the present invention.

[0029] Explanation of the reference numerals in the drawings:

[0030] 10, hub;

[0031] 20, hub body; 200, end; 202, inclined boss; 203, spoke; 2020, first water-drop-shaped notch; 20200, first concave notch; 2022, second water-drop-shaped notch; 20220, second concave notch; 206, first gasket; 208, freehub body; 2080, round opening; 2082, side plate; 2084, slot; 2086, inner boss; 2088, ratchet teeth; 210, second gasket; 212, axle core; 214, first bearing; 216, second bearing;

[0032] 30, top cover; 300, first conical guide notch; 302, first boss; 304, second boss; 306, third boss; 32, bottom cover; 320, second conical limit notch; 322, fourth boss; 324, fifth boss; 34, first ratchet ring; 340, first supporting part; 342, second supporting part; 36, second ratchet ring; 38a, flat wire compression spring a; 38b, flat wire compression spring b. Detailed implementation manners

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention.

[0034] In the description of the present invention, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more, unless otherwise specifically defined.

[0035] Referring to Figures 1-9 As shown, an integrated clutch connection device for a bicycle transmission system includes a hub 10; and spokes 203 connected between the hub 10 and a hub body 20.

[0036] The hub body 20 includes two symmetrically arranged ends 200. An inclined boss 202 is disposed around the outer wall of each end 200. A freewheel body 208 is connected to one of the ends 200. An inner boss 2086 and a continuous annular ratchet 2088 are provided on the inner wall of the freewheel body 208. A shaft core 212 is passed through the inside. A second gasket 210 is provided at the other end. A first gasket 206 is provided at the other end 200. The inclined boss 202 includes a first water-drop notch 2020 and a second water-drop notch 2022 formed symmetrically. Among them, both the first water-drop notch 2020 and the second water-drop notch 2022 include a first concave notch 20200 and a second concave notch 20220 for pulling the spokes 203. A plurality of round openings 2080 and a side plate 2082 are formed on the outer wall of the freewheel body 208. A slot 2084 is formed on the side plate 2082. A first bearing 214 and a second bearing 216 are sleeved on the outer wall of the shaft core 212.

[0037] The ratchet assembly forms an integrated meshing structure with the tower base 208 and includes: an integral ratchet ring elastically connected to the inner wall of the tower base 208 through a customized spring system; the customized spring system is composed of two identical flat wire compression springs 38a and 38b screwed together helically, forming a cross-sectional shape of a disc spring group, wherein the helical winding directions of the two flat wire compression springs 38a and 38b are opposite; after being screwed together, a composite spring module with non-linear stiffness characteristics is formed; the inner boss 2086 dynamically cooperates with the composite spring module, so that the meshing force of the integral ratchet ring is automatically adjusted according to the load change.

[0038] When stressed, the two flat wire compression springs 38a and 38b with opposite winding directions interact with each other to produce non-linear stiffness characteristics. The stiffness of the spring is dynamically adjusted as the load increases, satisfying the relationship: F = KP n (where 0.5 < n < 1 and K is the stiffness coefficient). This non-linear stiffness characteristic enables the spring to have a lower stiffness under small loads and can absorb more energy; while under large loads, the stiffness will increase significantly to provide stronger support force.

[0039] Furthermore, in the bicycle drive system of the present invention, there is a significant synergistic effect between the non-linear stiffness characteristic of the customized spring system and the progressive meshing mechanism of the integral ratchet structure. This synergistic effect is particularly prominent when the load suddenly increases, which can effectively absorb the impact energy and improve the stability and reliability of the system; when the load P suddenly increases, the stiffness of the customized spring system will experience a jump (ΔK). This rapid change in stiffness forms a time difference compensation with the progressive meshing characteristic (n = 0.67) of the integral ratchet. Specifically, the spring system can rapidly increase its stiffness within a short time to resist the sudden increase in load, while the integral ratchet gradually increases the meshing force through progressive meshing. This time difference compensation mechanism enables the impact energy to be absorbed in segments, avoiding damage to the system due to instantaneous overload. Through the non-linear stiffness characteristic, the spring system can absorb part of the impact energy at the initial stage of load increase, and then the progressive meshing of the integral ratchet further disperses the remaining impact energy. This segmented absorption mechanism significantly reduces the peak stress of the system under high load conditions, thereby improving the overall stability and durability of the system. This synergistic effect not only improves the impact resistance of the system but also extends the service life of the system. Through experimental verification (as shown in the following experiment), the impact energy absorption capacity of the drive system of the present invention is increased by about 30% compared with the traditional system when the load suddenly increases, and at the same time, the fatigue life of the system is increased by 20%.

[0040] Among them, the integrated meshing structure includes a top cover 30 and a bottom cover 32, and the inner walls of the top cover 30 and the bottom cover 32 are respectively formed with a first conical guide groove 300 and a second conical limit groove 320; wherein, one end of the top cover 30 is provided with a first boss 302, a second boss 304 and a third boss 306 stacked in sequence; one end of the bottom cover 32 is provided with a fourth boss 322 and a fifth boss 324 stacked in sequence.

[0041] The first conical guide slot 300 has a smaller angle than the second conical limit slot 320, and together they form a three-point positioning structure for the composite spring module. The smaller angle of the first conical guide slot 300 (e.g., 15°) provides initial guidance, allowing the composite spring module to smoothly enter the assembly position and avoid rigid collision between the spring wire and the slot edge. As the spring continues to move, the larger angle of the second conical limit slot 320 (e.g., 30°) forms a hard stop, achieving final positioning through increased contact pressure on the conical surfaces. Furthermore, the first conical guide slot 300 bears 20-30% of the radial force component, while the second conical limit slot 320 bears 70-80% of the axial force component. This force distribution effectively reduces the peak stress at the spring's maximum stress point by more than 30%. The difference in the two slots' angles creates a "wedge locking effect": when the system is subjected to a lateral impact, the slight deflection of the spring module causes the first and second slots to simultaneously generate opposing forces (F1sinα). <F2sinβ),自动矫正位置偏移,测试表明该结构可将轴向窜动量控制在0.05mm以内。

[0042] Flat wire compression springs 38a and 38b have a rectangular cross-section, a wire width-to-thickness ratio of 3:1 to 5:1, and a helix angle of 30° to 45°. This rectangular cross-section allows the spring to better disperse stress when subjected to force, reducing localized stress concentration and thus extending its service life. The optimized helix angle and wire width-to-thickness ratio allow the spring to absorb more energy under light loads, significantly improving the energy absorption capacity of the transmission system.

[0043] Furthermore, the ratio of the long side to the short side of the rectangular cross-section of the flat wire compression spring is 3.8:1±0.2, and the edges of the long sides are provided with a micro-chamfer of 0.1-0.2mm. This specific ratio combined with the edge treatment can stabilize the contact surface friction coefficient of the spring in the range of 0.12-0.15 when the spring is compressed and displaced by 5mm, reducing the friction fluctuation amplitude by 40% compared with the conventional rectangular cross-section (friction coefficient fluctuation range of 0.08-0.18).

[0044] The integral ratchet ring includes a first ratchet ring 34 and a second ratchet ring 36. The inner circumference of the integral ratchet ring is provided with support portions 340 and 342 that match the outer contour of the composite spring module, forming a three-dimensional force transmission interface. This design not only enhances the force transmission efficiency, but also ensures structural stability under high load conditions through precise geometric matching. The tooth profile of the continuous annular ratchet 2088 matches the restoring force curve of the composite spring module, so that the meshing impact force is buffered by the axial preload force of the spring. The integral ratchet ring 34 / 36 forms a full-circle meshing with the continuous annular ratchet 2088, ensuring that the ratchet can fit tightly with the ratchet at any position. This design eliminates the micro-wear problem of the traditional separate ratchet structure and significantly improves the stability and service life of the transmission system.

[0045] The inclination angle of the inner boss 2086 matches the deformation direction of the composite spring module.

[0046] Specifically, the present invention is further described with respect to the customized spring system as follows:

[0047] Implementation mechanism of spiral twisting structure:

[0048] The two springs (38a, 38b) are intertwined with opposite rotation directions (e.g., 38a is left-handed and 38b is right-handed), forming a "DNA double helix" topological structure (see Figure 9 ); Helix angle range: 30°-45° (optimal value 38°±2°); Crossover point density: 4-6 contact points per 10mm axial length.

[0049] Principle of nonlinear stiffness generation:

[0050]

[0051] This structure reduces the system load by 25% at 5mm displacement (compared to a traditional single spring) while increasing energy absorption by 28%.

[0052] Space-saving technology:

[0053] Axial size comparison:

[0054] Type Axial length required to generate 100N elastic force Traditional laminated disc spring 42mm The present invention 29mm (30.9% reduction)

[0055] Implementation method: Utilize radial expansion of the spirally twisted structure to compensate for axial deformation (radial expansion δ = 0.2 × compression ΔL).

[0056] Furthermore, the present invention further includes a manufacturing process for an integrated ratchet, and the process steps are as follows:

[0057] S1. Mold Design and Preparation: The cavity shrinkage rate is set at 1.2%. Based on the sintering shrinkage characteristics compensation of the Fe-Cr-Mo alloy, the cavity tooth profile is machined by electrical discharge machining, and the profile tolerance is controlled within ±0.01 mm.

[0058] S2. Mixing and Pretreatment: Fe-Cr-Mo alloy powder (composition: Cr 12 - 14 wt%, Mo 0.5 - 1 wt%, C 0.3 - 0.5 wt%) is used, and 0.5% zinc stearate lubricant is added. The mixture is mixed until the particle size distribution D50 = 45 μm.

[0059] S3. Isostatic Pressing: The pressing pressure is 600 MPa, the holding pressure time is 90 s, and the green density ≥ 7.2 g / cm 3 , and the local density difference of the tooth part ≤ 0.15 g / cm3.

[0060] S4. Sintering Treatment: The sintering temperature is 1120°C ± 10°C, the holding time is 90 min, under a hydrogen protection atmosphere (dew point ≤ -40°C), the oxygen content in the furnace < 50 ppm, the porosity after sintering ≤ 5%, and the grain size grade is ASTM 8 - 9.

[0061] S5. Finishing Cold Extrusion: The finishing pressure is 200 MPa, the mold is preheated to 150°C, the surface roughness of the tooth Ra ≤ 0.8 μm, and the cumulative pitch error ≤ 0.03 mm.

[0062] S6. Gradient Heat Treatment: Carburizing and Quenching: Carburize at 860°C for 2 h and oil quench to room temperature; Deep Cryogenic Treatment: Keep in liquid nitrogen at -196°C for 2 h and temper at 200°C for 4 h; Final Hardness: Tooth surface HRC 60 - 62, core HRC 40 - 42.

[0063] S7. Quality Inspection: Use a coordinate measuring machine to measure the tooth profile tolerance (tolerance 0.025 mm); Use magnetic particle flaw detection to check for surface cracks (defect size ≤ 50 μm); Conduct dynamic meshing tests (noise ≤ 65 dB under a load of 500 N).

[0064] Furthermore, in step S6, the carburizing and quenching process adopts segmented carbon potential control: carbon potential 1.2% for 0 - 30 min, carbon potential 0.8% for 30 - 90 min, and finally carbon potential 0.5% for 10 min, forming a gradient carbon concentration distribution (surface 0.8% C → core 0.3% C).

[0065] In step S7, acoustic emission technology is used to monitor the meshing process, and it is required that the energy ratio in the characteristic frequency range of 200 - 400 Hz ≥ 85%.

[0066] In summary, this process not only clearly demonstrates the manufacturing process, but also forms a complete technical closed-loop through parameter correlation design (such as the mold shrinkage rate of 1.2% corresponding to sintering shrinkage compensation) and cross-process quality control (such as the green density of 7.2 g / cm3 ensuring subsequent sintering densification).

[0067] Specifically, in order to better demonstrate the technical effects of the present invention, multiple groups of comparative tests were conducted in this case, and the test data were organized in tabular form. The following are the detailed test results:

[0068] Example 1: Comparative test on dynamic load performance

[0069] In order to verify the performance improvement of the present invention under dynamic load conditions, a comparative test between the traditional structure and the structure of the present invention was conducted in this case. The test results are shown in the following table:

[0070]

[0071] It can be seen from the table that the present invention is significantly superior to the traditional structure in terms of initial pre-tightening force, displacement load, ultimate load, stiffness change rate, and energy absorption.

[0072] Example 2: Ratchet engagement stability test

[0073] In order to evaluate the performance of the present invention in terms of ratchet engagement stability, a comparative test between the split ratchet and the integral ratchet of the present invention was conducted. The test results are shown in the following table:

[0074]

[0075]

[0076] The test results show that the present invention is significantly superior to the split ratchet in terms of axial runout, fretting wear rate, and meshing noise.

[0077] Example 3: Residual elastic force test

[0078] In order to further verify the durability of the present invention, a residual elastic force test was conducted. The test results are shown in the following table:

[0079] Number of cycles (in ten thousands) Residual elastic force of traditional structure (N) Residual elastic force of the present invention (N) 0 300 300 5 275 (8.3% attenuation) 290 (3.3% attenuation) 10 240 (20% attenuation) 280 (6.7% attenuation)

[0080] The data show that the present invention still maintains 93.3% of the initial elastic force after 100,000 cycles, which is significantly superior to the traditional structure. Moreover, the test shows that the double-helix interlocking structure improves the life of the spring by more than 40% under high cyclic loads through contact surface stress redistribution and fretting wear suppression, and at the same time increases the fatigue limit by 6 - 7%.

[0081] Working principle:

[0082] When the transmission system is under load, two flat wire compression springs 38a / 38b with opposite helix directions generate a non-linear stiffness response through an interlocking structure of mutual winding - in the initial stage, the springs deform independently to provide flexible cushioning, and as the load increases, friction occurs on the spring contact surfaces and they gradually interlock to form a rigid support; at the same time, this interlocking structure pushes the integral ratchet ring to achieve full-circumference engagement with the continuous annular ratchet teeth 2088 in the tower base 208, and the axial pre-tightening force of the spring is converted into a uniform radial meshing force through the specially designed supporting parts 340 / 342 on the inner peripheral surface of the ratchet ring. This dual-action mechanism enables the system to adapt to load changes through spring interlocking and eliminate the fretting wear of the traditional separated structure by means of the integral ratchet, ultimately achieving stable and efficient power transmission of the transmission system at any meshing position.

[0083] The above is only the preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An integrated clutch connection device for a bicycle transmission system, characterized in that, include Wheel hub (10); A hub body (20), the hub body (20) comprising two symmetrically arranged end portions (200), the outer wall of each end portion (200) being provided with a surrounding inclined boss (202), one of the end portions (200) being connected to a tower base (208), the inner wall of the tower base (208) being provided with an inner boss (2086) and a continuous annular ratchet (2088), an inner shaft core (212) being passed through, the other end being provided with a second liner (210), and the other end portion (200) being provided with a first liner (206); Spokes (203) connected between the wheel hub (10) and the hub body (20); A ratchet assembly, forming an integrated meshing structure with the tower base (208), comprises: an integral ratchet ring, elastically connected to the inner wall of the tower base (208) via a customized spring system; The customized spring system is composed of two identical flat wire compression springs (38a) and a flat wire compression spring (38b) that are screwed together to form a disc spring group cross-section, wherein: The spiral directions of the two flat wire compression springs (38a) and the flat wire compression spring (38b) are opposite; After being tightened together, a composite spring module with nonlinear stiffness characteristics is formed; The inner boss (2086) is dynamically matched with the composite spring module so that the meshing force of the integral ratchet ring is automatically adjusted as the load changes.

2. The integrated clutch connection device for a bicycle drive system according to claim 1, characterized in that, The flat wire compression spring (38a) and the flat wire compression spring (38b) have rectangular cross sections, a line width to thickness ratio of 3:1 to 5:1, and a helical angle of 30° to 45°.

3. An integrated clutch connection device for a bicycle transmission system according to claim 1, characterized in that, The integral ratchet ring comprises a first ratchet ring (34) and a second ratchet ring (36); the inner circumference of the integral ratchet ring is provided with a first supporting portion (340) and a second supporting portion (342) matching the outer contour of the composite spring module, forming a three-dimensional force transmission interface.

4. An integrated clutch connection device for a bicycle drive system according to claim 1, characterized in that, The tooth profile of the continuous annular ratchet (2088) matches the restoring force curve of the composite spring module, so that the engagement impact force is buffered by the axial preload force of the spring.

5. An integrated clutch connection device for a bicycle drive system according to claim 1, characterized in that, The inclination angle of the inner boss (2086) matches the deformation direction of the composite spring module.

6. The integrated clutch connection device for a bicycle transmission system according to claim 1, characterized in that, The inclined boss (202) comprises a first water drop notch (2020) and a second water drop notch (2022) that are symmetrically formed; wherein the first water drop notch (2020) and the second water drop notch (2022) both comprise a first inner recess (20200) and a second inner recess (20220) for pulling the spoke (203).

7. An integrated clutch connection device for a bicycle transmission system according to claim 1, characterized in that, The outer wall of the tower base (208) is formed with a plurality of circular openings (2080) and side plates (2082), and a groove (2084) is formed on the side plates (2082).

8. An integrated clutch connection device for a bicycle drive system according to claim 1, characterized in that, The outer wall of the shaft core (212) is sleeved with a first bearing (214) and a second bearing (216).

9. An integrated clutch connection device for a bicycle transmission system according to claim 1, characterized in that, The integrated engagement structure comprises a top cover (30) and a bottom cover (32), wherein the inner walls of the top cover (30) and the bottom cover (32) are respectively formed with a first tapered guide notch (300) and a second tapered limiting notch (320); wherein, One end of the top cover (30) is provided with a first boss (302), a second boss (304) and a third boss (306) stacked in sequence; One end of the bottom cover (32) is provided with a fourth boss (322) and a fifth boss (324) stacked in sequence.

10. An integrated clutch connection device for a bicycle transmission system according to claim 9, characterized in that, The taper angle of the first conical guide notch (300) is smaller than the taper angle of the second conical limit notch (320), and the two together form a three-point positioning structure for the composite spring module.

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