Piston Assembly Resin Seal Biasing Cylinder Bore Contact
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Solution Overview
Problem
Existing piston assemblies for human-powered vehicles, such as bicycles, face challenges in achieving improved sliding contact with cylinder bores while maintaining firm contact and optimizing manufacturing costs, particularly in hydraulic braking systems.
Innovation Solution
A piston assembly featuring a primary seal made of resin material with a biasing part, often made of rubber, which is designed to outwardly bias the primary lip portion for enhanced contact with the cylinder bore, and a secondary seal to improve sliding and sealing performance, with components made from materials like polytetrafluoroethylene and polyimide-filled polytetrafluoroethylene to reduce costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a resin material is used for the primary seal body, then sliding contact with the cylinder bore is improved, but firm contact with the cylinder bore deteriorates
Solution Approach 1:
The patent employs composite material construction where the primary seal body is made of resin material for improved sliding contact, while a biasing part made of elastic material (such as rubber) is integrated to maintain firm contact with the cylinder bore. This composite approach combines the low-friction properties of resin with the elastic recovery properties of rubber to resolve the contradiction between smooth sliding and reliable sealing contact.
Solution Approach 2:
The patent changes the physical parameters of the seal system by introducing a biasing part that applies radial outward force on the primary lip portion. This parameter change (applying pre-compression force) ensures that the resin seal body maintains sufficient contact pressure with the cylinder bore despite its inherently lower friction characteristics, thereby preserving reliable sealing while enabling smooth sliding motion.
2Reliability
If a biasing part is added to outwardly bias the primary lip portion, then firm contact with the cylinder bore is maintained, but device complexity increases
Solution Approach 1:
The patent merges the biasing function with the seal body by integrating the biasing part directly onto the primary seal body. This combination eliminates the need for separate external biasing mechanisms, reducing overall device complexity while still achieving the goal of maintaining firm contact between the seal and cylinder bore through the radial outward force applied to the primary lip portion.
3Ease of manufacture
If resin and rubber materials are used, then manufacturing costs are reduced, but sealing performance may deteriorate
Solution Approach 1:
The patent applies local quality differentiation by using resin material for the main body of the primary seal where low friction and cost-effectiveness are priorities, while using elastic rubber material specifically for the biasing part where sealing force and reliability are critical. This localized material assignment optimizes both manufacturing cost and sealing performance by matching material properties to functional requirements in different regions of the seal assembly.
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 piston assembly achieves improved sliding contact and reduced manufacturing costs by using resin and rubber materials, ensuring effective sealing and movement within the cylinder bore, enhancing the performance of hydraulic braking systems in human-powered vehicles.
Implementation Method 1
The biasing part is made of a rubber material and is configured to be in contact with an outer circumferential surface of the main body to outwardly bias the primary lip portion
Implementation Method 2
it is possible to provide a piston assembly that has an improved sliding contact with the cylinder bore by using a resin material for the primary seal
Data Source
AI summary
A piston assembly is provided for a human-powered vehicle. The piston assembly includes a main body and a primary seal. The main body is configured to be movable from a rest position to an actuated position along an actuation direction in a cylinder bore. The primary seal includes a primary seal body arranged on the main body. The primary seal body is made of a resin material. The primary seal body has a primary lip portion configured to be in contact with the cylinder bore in an arranged state where the piston assembly is arranged in the cylinder bore. The primary seal further includes a biasing part configured to be in contact with an outer circumferential surface of the main body to outwardly bias the primary lip portion of the primary seal body in the arranged state.