Deflected Tension Spring Structure for Fatigue-Resistant Long Stroke
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Solution Overview
Problem
Traction devices with tension springs used in deceleration and acceleration systems are prone to breakage due to high load cycles, limiting their lifespan.
Innovation Solution
Designing a tension spring with a total stroke of at least 50% of its nominal length, featuring areas of high and low spring stiffness, where the high stiffness area is at the deflection pulley, and a quotient of the average deflection radius to the differential deflection of the outer and inner spring areas per coil is greater than 50, ensuring the spring can withstand a high number of load cycles without breaking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tension spring is used in a traction device with high load cycles, then the device can achieve sufficient strength and durability, but the spring is prone to breakage due to fatigue from repeated loading
Solution Approach 1:
The tension spring is designed with varying stiffness along its length, featuring a first region with higher stiffness and a second region with lower stiffness. This local quality variation allows different sections of the spring to perform different functions: the stiffer first region provides structural strength and maintains proper geometry under load, while the more flexible second region absorbs fatigue stresses through greater deformation, thereby preventing breakage and improving overall reliability.
2Length of moving object
If the tension spring has a large total stroke to accommodate high displacement requirements, then the device achieves greater mobility and range of motion, but the spring becomes more susceptible to breakage under repeated cycling
Solution Approach 1:
By creating a stiffness gradient along the spring length, the invention allows the spring to achieve large total stroke while maintaining reliability. The lower stiffness region accommodates the majority of the displacement through elastic deformation, while the higher stiffness region maintains structural integrity. This local differentiation enables the spring to handle large strokes without the entire spring being equally vulnerable to fatigue failure.
3Ease of manufacture
If the tension spring is designed with uniform stiffness throughout, then the manufacturing process is simpler and more cost-effective, but the spring cannot distribute stress evenly leading to premature failure
Solution Approach 1:
The spring incorporates regions of different stiffness through variations in coil geometry, such as different coil diameters or pitch in different sections. While this requires more complex manufacturing compared to uniform springs, modern coil spring manufacturing techniques can accommodate these variations efficiently. The benefit of even stress distribution and extended service life outweighs the moderate increase in manufacturing complexity.
Solution Approach 2:
The spring is effectively segmented into functional zones with different mechanical properties. The first region with higher stiffness and the second region with lower stiffness act as distinct functional segments that work together. This segmentation allows each region to be optimized for its specific role in stress distribution and deformation, improving overall reliability while remaining manufacturable through standard progressive coil spring processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution significantly extends the service life of the tension spring by distributing stress evenly, allowing it to handle a high number of load cycles without failure, while maintaining a compact design.
Implementation Method 1
a tension spring (53), in particular a tension spring made in one piece, is provided with two areas (56, 57) having different winding diameters
Implementation Method 2
a deflection device or deflection roller (71) is provided, on which an inner area (58) of the tension spring (53) rests
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a tensioning device comprising a tension spring that rests against a diversion or deflection roller while at least partially being wound around it, to a combined deceleration/acceleration device comprising said tensioning device and to a guide system comprising said deceleration/acceleration device. The total spring stroke of the tension spring is at least 50% of its nominal stroke. The tension spring comprises at least one zone of high spring rigidity and at least one zone of low spring rigidity. The zone of high spring rigidity rests against the diversion or deflection roller. In the zone of high spring rigidity, the quotient of the average diversion or deflection radius and the differential stroke of the outer and inner spring zone per spring coil is greater than 50. The invention provides a device which essentialy rules out spring fracture.