Segmented Bicycle Sprockets for Smooth Enclosed Gear Shifting
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Solution Overview
Problem
Current bicycle gearbox technologies face challenges in efficiently shifting gears while protecting the gearing system from dirt and moisture, and optimizing weight distribution for improved bicycle handling.
Innovation Solution
The implementation of segmented sprockets with independently movable gear segments and a shifting system that uses a power transfer mechanism, such as a belt or chain, to rotate coaxial gears, allowing for sequential movement of gear segments out of the plane of the power transfer mechanism using radially transitionable sliders and actuators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional enclosed gearbox is used, then protection from dirt and moisture is improved, but gear shifting efficiency and smoothness deteriorate
Solution Approach 1:
The first gear is divided into multiple independently movable gear segments that can be sequentially shifted out of the plane. This segmentation allows the chain to engage with different segments smoothly during shifting, maintaining efficient power transfer while keeping the gearbox enclosed and protected from contaminants.
Solution Approach 2:
The gear segments are designed to be dynamically movable into and out of the plane rather than fixed. This dynamic capability enables smooth transitions during gear shifting, allowing the chain to naturally follow the moving segments without lateral displacement, thereby maintaining shifting efficiency within the protected enclosed gearbox.
2Adaptability or versatility
If gear segments are moved laterally, then gear ratio changing is achieved, but chain displacement and friction increase
Solution Approach 1:
Instead of moving gear segments laterally in the plane of the chain, the invention moves segments in a different dimension - perpendicular to the chain plane. This vertical/out-of-plane movement allows gear ratio changes without lateral chain displacement, minimizing friction and energy loss while achieving versatile gear ratio changes.
3Ease of operation
If segmented sprockets with independent movement are used, then gear shifting smoothness is improved, but device complexity increases
Solution Approach 1:
The gear segments are designed to move automatically under the influence of the chain tension and gravitational forces during pedaling. The segments shift smoothly without requiring complex external actuation mechanisms, as the system uses the existing operational forces (chain tension, rider input) to drive the shifting action, thereby maintaining ease of operation while limiting complexity growth.
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
This solution enables smooth and efficient gear shifting without displacing the chain or belt laterally, maintaining protection from dirt and moisture, and optimizing weight distribution for improved bicycle handling and flexibility in gearing choices.
Implementation Method 1
each of the sliders has a pair of ramped cam surfaces and is operatively coupled to a corresponding one of the gear segments of the first gear; extending a first pin of a multi-pin actuator, wherein the multi-pin actuator is stationary with respect to the rotating sliders, such that the first pin is in a path of a first one of the ramped cam surfaces
Data Source
AI summary
A method for shifting a segmented gear may include rotating a gear cluster including a first gear and a coaxial second gear using a power transfer mechanism (e.g., a belt or a chain). The power transfer mechanism defines a plane and is wrapped partially around the first gear. and wherein the first gear has a plurality of gear segments independently movable (e.g., pivotable or translatable) into and out of the plane. A plurality of radially transitionable sliders are rotated in tandem with the first gear, and each of the sliders is operatively coupled to a corresponding one of the gear segments of the first gear. In sequence, each segment of the first gear is moved out of the plane of the power transfer mechanism by urging the slider in a radial direction using a segment actuator, such that the power transfer mechanism wraps at least partially around the second gear.