Variable Rate Brake Linkage for Bicycle Hydraulic Systems
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Solution Overview
Problem
Hydraulic brake systems for bicycles suffer from a significant 'dead band' where no braking forces are generated initially, requiring excessive lever travel, and lack adjustable mechanisms to minimize this gap without affecting piston travel rate or increasing complexity and weight.
Innovation Solution
A brake assembly with a variable rate linkage system that includes a cam link and follower link to produce a non-linear lever blade stroke, allowing for adjustable dead band without affecting the piston actuation rate, and a piston adjustment mechanism to fine-tune brake force across the lever stroke.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a linear rate of travel linkage is used, then the structure is simple, but excessive dead band occurs requiring significant lever travel before braking occurs
Solution Approach 1:
The patent applies a variable rate linkage mechanism that dynamically changes the lever blade stroke rate during actuation. The linkage transitions from a higher rate at initial stroke to a lower rate near full stroke, optimizing both dead band reduction and brake force distribution without requiring complex additional components
Solution Approach 2:
The invention changes the stroke rate parameter throughout the lever travel distance. By varying the mechanical advantage ratio along the lever stroke, the system achieves reduced dead band while maintaining structural simplicity and avoiding excessive complexity
2Loss of time
If adjustable mechanisms are added to minimize dead band, then dead band is reduced, but device complexity and weight increase
Solution Approach 1:
The patent combines the dead band adjustment function with the existing variable rate linkage mechanism. The adjustable rest position feature is integrated into the same linkage structure that provides variable stroke rate, eliminating the need for separate adjustment mechanisms and reducing overall complexity
Solution Approach 2:
The variable rate linkage serves multiple functions simultaneously: it reduces dead band, provides adjustable rest position, and optimizes brake force distribution. This multi-functionality eliminates the need for separate dedicated adjustment mechanisms, maintaining structural simplicity
3Loss of time
If variable rate linkage is used to reduce dead band, then dead band is minimized, but the piston travel rate relative to lever travel is affected
Solution Approach 1:
The variable rate linkage dynamically adjusts the piston travel rate throughout the lever stroke. The mechanism provides higher piston travel rate initially to reduce dead band, then transitions to appropriate rates for optimal brake force application, maintaining overall system performance
Solution Approach 2:
The invention changes the piston travel rate parameter as a function of lever stroke position. By varying the mechanical advantage along the stroke, the system optimizes both dead band reduction and piston actuation rate without compromising brake performance
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 system reduces dead band, enhances brake performance by varying brake force, and allows for adjustable dead band without increasing complexity or weight, providing improved modulation and control with reduced manufacturing costs.
Implementation Method 1
the cam and follower links interact to produce a variable rate of travel of the piston assembly relative to the travel of the lever
Implementation Method 2
a pushrod is disposed between the follower link and the piston assembly
Implementation Method 3
A piston assembly is received and axially guided within the fluid chamber
Data Source
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AI summary
A brake assembly for a hydraulic brake system of a handlebar-steered vehicle, the brake assembly including a housing mountable to a handlebar of the vehicle and having a chamber formed therein. The brake assembly is provided with a variable rate linkage. A piston assembly is received and axially guided within the chamber and is provided with a piston adjustment mechanism that does not affect the function of the variable rate linkage.