What are Torsion Springs?
Torsion springs are mechanical components designed to store and release energy through twisting or torsional deformation. They consist of a wire or bar coiled into a helical shape, with the ends fixed or constrained in a specific manner. When torque is applied, the spring twists, storing potential energy, and when the torque is released, the spring unwinds, releasing the stored energy.
Mechanics of Torsion Springs
- They exhibit a linear spring characteristic, allowing simple adaptation to lever mechanisms.
- They can develop high spring loads while occupying minimal space, enabling compact designs.
- The spring constant depends on the material’s shear modulus, wire diameter, coil diameter, and number of active coils.
- Friction between coils and end effects can introduce nonlinearity and hysteresis in the torque-displacement response.
- Close-wound torsion springs experience friction between coils, leading to different natural frequencies for forward and backward strokes.
Types of Torsion Springs
Classification Based on Spring Geometry
They can be classified based on their geometric shape and configuration:
- Helical torsion springs: Made by coiling a wire into a helical shape, with straight ends for applying torque.
- Spiral torsion springs: Formed by winding a flat metal strip into a spiral plane.
- Elliptical torsion springs: Consist of slightly bent leaf springs mounted in pairs against each other.
- Parabolic torsion springs: Use leaf springs with strength decreasing parabolically from the middle to the ends.
- Wave torsion springs: Rings made of wavy flat wire that bends under load.
Classification Based on Cross-Section
The cross-sectional shape of the torsion spring wire or strip also serves as a classification criterion:
- Rectangular or square cross-section
- Trapezoidal cross-section
- Circular cross-section (conventional round wire)
Classification Based on Winding Direction
They can be classified based on the direction of winding:
- Right-hand wound springs
- Left-hand wound springs
Classification Based on End Configurations
The end configurations of them also vary, leading to different classifications:
- Plain ends: Straight wire ends for torque application.
- Formed ends: Ends bent into specific shapes like hooks or eyes for attachment.
- Slotted ends: Slots cut into the ends to reduce stress concentrations.
Other Classifications
- Open or closed coils: Based on the spacing between adjacent coils.
- Constant or variable pitch: Based on whether the coil spacing is uniform or not.
- Single or multi-stage: Multi-stage springs have different coil diameters along the length
Applications of Torsion Springs
Automotive Industry
They are widely used in automotive applications, including:
- Suspension systems: Torsion bars are employed as an alternative to coil springs in vehicle suspensions, providing a compact and lightweight solution.
- Door hinges: They are used in door hinges to counterbalance the weight of the door and facilitate smooth opening and closing.
- Clutch and brake systems: They are utilized in clutch and brake mechanisms to provide the necessary torque and damping.
Aerospace Industry
They find applications in aerospace systems, such as:
- Aircraft landing gear: Torsion bars are used in the landing gear systems of aircraft to absorb shock and provide a smooth landing.
- Satellite and spacecraft mechanisms: They are employed in various mechanisms, such as solar panel deployment and antenna positioning, due to their compact size and high energy storage capacity.
Industrial Machinery
They are essential components in various industrial machinery, including:
- Conveyor systems: They are used in conveyor belt tensioning mechanisms to maintain proper belt tension.
- Printing and packaging machinery: They are utilized in various mechanisms, such as paper feed and cutting systems.
- Textile machinery: They are employed in textile machinery, such as looms and knitting machines, to provide tension and control.
Consumer Products
Torsion springs are also found in various consumer products, such as:
- Household appliances: Torsion springs are used in appliances like washing machines, dishwashers, and refrigerators for door mechanisms and damping.
- Furniture: Torsion springs are utilized in reclining chairs, sofa beds, and other furniture mechanisms.
- Toys and sporting goods: Torsion springs are employed in toys, exercise equipment, and sporting goods for mechanisms like spring-loaded launchers and tension adjustment.
Micromechanical Applications
They find applications in micromechanical devices, such as:
- Micro-electromechanical systems (MEMS): They are used in MEMS devices for pivoting elements, such as mirrors for optical switching or scanning.
- Microrobots and micromanipulators: They are employed in microrobotic systems for precise positioning and actuation.
Application Cases
| Product/Project | Technical Outcomes | Application Scenarios |
|---|---|---|
| Tesla Autopilot | Using model quantisation techniques, inference speed increased by 4 times, and power consumption reduced by approximately 2 times. | Resource-constrained edge devices, such as in-vehicle systems requiring quick response. |
| Google BERT | Adopting optimised TensorFlow Lite, quantisation and knowledge distillation techniques, latency reduced by around 10 times, model size shrank to 1/4 of the original size. | Real-time online services, such as search engines needing to process and respond to user queries swiftly and accurately. |
| NVIDIA Clara | Leveraging AI and advanced visualisation, it enables faster and more accurate detection, diagnosis and treatment of diseases, reducing diagnostic errors and improving patient outcomes. | Healthcare facilities, assisting radiologists and clinicians in medical imaging analysis and clinical decision support. |
| OpenAI GPT-3 | With its massive language model and few-shot learning capabilities, it can generate human-like text, code, and creative content with minimal input, revolutionising various NLP tasks. | Content creation, code generation, question answering, and any task involving natural language processing and understanding. |
| Boston Dynamics Spot | Utilising advanced robotics and AI, it can navigate challenging terrain, carry payloads, and perform autonomous inspection tasks in hazardous environments, enhancing safety and efficiency. | Industrial inspection, construction sites, public safety, and any scenario requiring mobile robotic assistance in dangerous or inaccessible areas. |
Latest Technical Innovations of Torsion Springs
Torsion Spring Structure Optimization
- Varying coil diameter along the spring axis to reduce friction, hysteresis, and undefined spring characteristics. The coil diameter gradually changes from larger to smaller and back, preventing coils from snapping over the centering diameter.
- Symmetrical spring structure with defined pitch and coil diameter for improved linearity and reproducibility.
- Non-cylindrical spring shapes like conical or parabolic profiles for space-saving and high spring forces.
Torsion Spring Materials and Manufacturing
- Advanced materials like shape memory alloys for improved fatigue life and recoverable deformation.
- Specialized coatings to enhance wear resistance, corrosion protection, and lubricity.
- Innovative manufacturing techniques like additive manufacturing for complex geometries and integrated designs.
Multi-Functional Torsion Springs
- Combination of torsion and compression/tension spring functions in a single component for compact designs.
- Integration of torsion springs with other mechanisms like levers or cams for space-efficient actuation systems.
Variable Stiffness Torsion Springs
- Adjustable spring stiffness through active or passive mechanisms for vibration damping and dynamic load adaptation.
- Nested torsion spring assemblies with varying stiffness characteristics for wider operating ranges.
Micromechanical Torsion Springs
Miniaturized torsion springs fabricated using MEMS technologies for micro-positioning and actuation 11.
Optimized cross-sections and slotted designs to improve linearity and prevent fracture in microscale torsion springs.
Computational Modeling and Optimization
- Advanced simulation techniques like finite element analysis for accurate prediction of spring behavior.
- Computational design optimization algorithms for weight reduction and performance enhancement.
- Modeling of friction, end effects, and boundary conditions for improved torsion spring analysis
Technical Challenges of Torsion Springs
| Torsion Spring Structure Optimization | Optimising the torsion spring structure to reduce friction, hysteresis, and undefined spring characteristics by varying the coil diameter along the spring axis, employing symmetrical spring designs with defined pitch and coil diameter, and utilising non-cylindrical shapes like conical or parabolic profiles. |
| Torsion Spring Materials and Manufacturing | Utilising advanced materials like shape memory alloys to improve fatigue life and enable recoverable deformation, applying specialised coatings to enhance wear resistance, corrosion protection, and lubricity, and implementing innovative manufacturing techniques like additive manufacturing for complex geometries and integrated designs. |
| Multi-Functional Torsion Springs | Developing torsion springs that combine the functions of a coil spring for generating vertical elasticity and a torsion spring for generating horizontal elasticity, thereby reducing the number of parts and the overall size of the structure. |
| Variable Stiffness Torsion Springs | Designing torsion springs with adjustable spring constants to achieve variable stiffness, enabling their application in gimballed payloads, sensors, telescopes, and electronic devices on platforms like space shuttles or space stations. |
| Torsion Spring Design for Micromechanical Applications | Developing torsion springs with square, rectangular, or trapezoidal cross-sections and slots oriented orthogonally and along the longitudinal axis to improve the linearity of the spring characteristic for micromechanical applications. |
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