Planetary Gearbox Torsion Spring Torque Limiting
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Solution Overview
Problem
Existing mechanical systems face challenges in preventing overloading of output shafts due to excessive torque, which can lead to mechanical part damage, and require complex reset mechanisms after overload conditions are removed.
Innovation Solution
A gearbox incorporating a planetary gearset coupled with a constant torsion spring that limits torque output by winding the spring when excessive torque is applied, thereby preventing damage and automatically resetting the positional relationship between input and output shafts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional torque limiting mechanism is used, then output torque can be limited to prevent damage, but the system requires complex reset mechanisms after overload
Solution Approach 1:
The constant torsion spring automatically resets the system by unwinding after the overload condition is removed, eliminating the need for external reset mechanisms. The spring's inherent elastic properties enable self-service operation where the system resets itself without additional components or manual intervention.
Solution Approach 2:
The system uses the physical parameter changes of the constant torsion spring (torsional deformation and recovery) to achieve torque limiting and automatic resetting. The spring's ability to store and release mechanical energy through parameter changes enables the simplified operation.
2Device complexity
If a constant torsion spring is used to limit torque, then the system automatically resets after overload, but the spring must be strong enough to withstand maximum torque
Solution Approach 1:
The constant torsion spring is pre-loaded during normal operation to a controlled amount, storing elastic energy in advance. This preliminary action allows the spring to respond immediately when overload occurs and automatically reset the system without requiring excessive strength, as the spring only needs to withstand the pre-loaded torque plus the overload threshold.
3Use of energy by moving object
If the ring gear is allowed to move during overload, then the spring can wind to store energy, but the output shaft may experience uncontrolled movement
Solution Approach 1:
The system dynamically transitions between two states: during normal operation, the ring gear is constrained to maintain stable output shaft positioning; during overload, the ring gear is allowed to move to wind the spring and store energy. This dynamic behavior enables both energy storage and positional control at different operational phases.
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 effectively limits output torque to prevent mechanical damage and automatically resets the system to its original position after an overload, enhancing system reliability and reducing the need for complex reset mechanisms.
Implementation Method 1
A constant torsion spring is coupled to a ring gear of the planetary gearset. The constant torsion spring is capable of preventing the ring gear from moving when a torque at the output shaft is below a threshold. The ring gear winds the constant torsion spring in response to the torque exceeding the threshold.
Data Source
AI summary
A gearbox includes a planetary gearset, an input shaft coupled to a sun gear of the planetary gearset, and an output shaft coupled to planet gears of the planetary gearset via a carrier. A constant torsion spring is coupled to a ring gear of the planetary gearset. The constant torsion spring is capable of preventing the ring gear from moving when a torque at the output shaft is below a threshold. The ring gear winds the constant torsion spring in response to the torque exceeding the threshold.