Bicycle Bottom Bracket Shaft With Through-Cavity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing bottom bracket assemblies of bicycles suffer from issues with dirt and corrosive substances accumulating inside the hollow shaft, leading to damage over time, due to the presence of screws that fix the crank arms to the shaft, which act as obstructing elements.
Innovation Solution
The design incorporates a through-cavity extending along the longitudinal direction of the shaft and crank arms, eliminating obstructions and allowing easy passage of dirt and corrosive substances, with coupling means arranged radially outer to prevent accumulation, and a conical surface to facilitate their exit, made from materials like aluminum alloy for the shaft and composite materials for the crank arms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If screws are used to fix crank arms to shaft or to fix together shaft elements, then the crank arms can be securely attached to the shaft, but dirt and corrosive substances accumulate on the screws causing damage over time
Solution Approach 1:
The patent removes the screws from the internal structure of the shaft and relocates them to the external surface. This extraction eliminates the obstructing elements from the interior cavity where dirt and corrosive substances would accumulate, while maintaining the attachment function through externally positioned fastening elements that do not interfere with the internal through-cavity.
Solution Approach 2:
The fastening elements are repositioned from a radial/internal dimension (inside the shaft) to an axial/external dimension (on the surface of the shaft). This dimensional relocation allows the screws to perform their fastening function while being accessible from the outside, preventing accumulation of harmful substances in the internal cavity.
2Weight of moving object
If hollow shafts are used to reduce overall weight, then the bicycle weight is reduced, but dirt and corrosive substances can still accumulate inside the shaft
Solution Approach 1:
The patent extracts the fastening screws from the internal cavity of the hollow shaft and relocates them to the external surface. This maintains the weight-saving benefits of the hollow shaft design while eliminating the accumulation problem by ensuring all fastening elements are accessible from the outside, allowing dirt and corrosive substances to pass through the through-cavity without depositing on internal obstacles.
Solution Approach 2:
The shaft is designed with different properties in different locations: the internal through-cavity maintains a clean, obstruction-free path for weight reduction and corrosion resistance, while the external surface accommodates fastening elements where dirt accumulation is less critical and can be managed through accessibility for cleaning and maintenance.
3Ease of manufacture
If screws are arranged in radially inner position with respect to the shaft, then the crank arms can be fixed to the shaft, but the screws act as obstructing elements inside the shaft
Solution Approach 1:
The patent extracts the fastening screws from the radially inner position inside the shaft and relocates them to the radially outer position on the shaft surface. This eliminates the internal obstructions that would complicate the device structure and interfere with the through-cavity, while maintaining the ease of crank arm fixation through the externally positioned fastening elements.
Solution Approach 2:
The fastening elements are repositioned from a radial/internal dimension to an axial/external dimension. This dimensional change removes the screws from the internal cavity space, simplifying the device structure by eliminating internal obstructions while preserving the crank arm fixation function through externally accessible fastening points.
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 design significantly reduces the deposition of dirt and corrosive substances within the shaft, facilitates easy cleaning, and enhances the durability of the components by preventing damage from such substances, while allowing for precise axial adjustment of the crank arms.
Implementation Method 1
a through-cavity extending along said longitudinal direction and entirely passing without any obstructions through said left crank arm, said shaft and said right crank arm
Implementation Method 2
a conical surface to facilitate their exit
Implementation Method 3
The rotation of the shaft with respect to the bicycle frame is achieved by fitting a pair of rolling bearings on the shaft
Implementation Method 4
first coupling means of the left crank arm with the shaft, the aforementioned first coupling means being arranged in a radially outer position with respect to the through-cavity
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a bottom bracket assembly (1) of a bicycle, comprising a shaft (2) having an axis (X-X) extending along a longitudinal direction, a pair of crank arms (30, 40), each one associated with a respective end portion (3, 4) of said shaft (2), a pair of bearings (31, 41) adapted to support said shaft (2) in rotation with respect to a housing box (10) of the bottom bracket assembly (1) provided in a bicycle frame, adjustment means (8) for adjusting the axial position of at least one crank arm of said pair of crank arms (30, 40) with respect to said pair of bearings (31, 41). The adjustment means (8) are axially arranged between said at least one crank arm of said pair of crank arms (30, 40) and a respective bearing of said pair of bearings (31, 41) and comprise a first service ring nut (8a) in axial abutment with said respective bearing (31, 41), a second service ring nut (8b) coupled with said first service ring nut (8a) and in axial abutment with said at least one crank arm of said pair of crank arms (30, 40), and means (8c) for blocking the axial position of said second service ring nut (8b) with respect to said first service ring nut (8a). The first service ring nut (8a) comprises an external threading (8a1) and the second service ring nut (8b) comprises an internal threading (8b1) engaged with said external threading (8a1).