Shiftable Bottom Bracket Gear Train Torque Lock
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Solution Overview
Problem
Conventional shiftable bottom bracket gear trains require a torque lock that necessitates a specific frame shape for attachment, limiting the flexibility in installing the gear train within a bicycle's bottom bracket tube independent of the frame structure.
Innovation Solution
A bottom bracket gear train design featuring a torque lock with a screw connection between the gear wheel's flanged exterior thread and the bottom bracket tube's interior thread, allowing for secure rotation blocking without additional attachment to the rear-wheel fork, and incorporating various torque lock mechanisms such as screws, pins, cams, or a conical ring for versatility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a torque lock is attached to the rear-wheel fork, then torque support is provided, but the frame must have a specific shape which limits design flexibility
Solution Approach 1:
The torque lock function is extracted from the rear-wheel fork attachment and relocated to the bottom bracket tube. The torque lock lever arm is now integrated into the gear train housing and transfers torque reactions directly to the bottom bracket tube, eliminating the need for rear-wheel fork attachment points and enabling universal installation on any bicycle frame regardless of rear-wheel fork design.
2Strength
If a torque lock with lever arm attached to rear-wheel fork is used, then torque reactions are supported, but additional installation elements on the rear-wheel fork are required
Solution Approach 1:
The torque lock function is merged with the gear train housing by integrating the lever arm directly into the housing structure. This consolidation eliminates the need for separate installation elements on the rear-wheel fork, as the torque lock now uses the bottom bracket tube itself as the mounting structure, reducing overall device complexity.
3Ease of manufacture
If the torque lock is integrated in the housing, then installation is simplified, but the housing structure becomes more complex
Solution Approach 1:
The housing is segmented into functional modules: the lever arm is designed as a separate component that can be independently manufactured and then assembled into the gear train housing. This modular segmentation allows the lever arm to be optimized for torque lock function while the housing provides structural support, simplifying both manufacturing and installation while managing overall complexity.
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
Enables the gear train to be installed in the bottom bracket tube regardless of the frame structure, eliminating the need for additional installation elements and ensuring secure torque support, facilitating easy installation and centering while preventing lubricant leakage.
Implementation Method 1
A torque lock arranged between the gear wheel and the bottom bracket tube is constructed with a screw connection between the exterior thread of the flanged portion of the gear wheel and the interior thread of the bottom bracket tube so as to block the gear wheel from rotating relative to the bottom bracket tube
Data Source
AI summary
The shiftable bottom bracket gear train according to the invention for a bicycle or the like comprises a bottom bracket tube, a gear train housing having an associated sprocket and a disk arranged parallel thereto, and a drive shaft, which penetrates the bottom bracket tube in the axial direction and is operatively connected to pedal cranks and in which a shifting axle is arranged, which is connected to a coupling piece and can be actuated from the outside by means of a shifting element. In the shiftable bottom bracket gear train, the torque support of the gear train engages on the bottom bracket tube (1) or on an adapter (2) inserted in the bottom bracket tube (1), and is implemented by using screws (8) or screw connections (4,5,12), pins (9, 17), cams (14), or clamps (13).