Brake Piston Adjuster Assembly With Nested Crushable Tubes
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Solution Overview
Problem
Existing brake systems face challenges in maintaining the correct piston stroke length due to wear of friction elements, leading to increased clearance and longer engagement times, which require periodic manual adjustments and are not effectively addressed by current automatic adjuster designs, especially for longer strokes without increasing the axial envelope of the assembly.
Innovation Solution
A piston assembly with an adjuster assembly that includes an inner and outer crushable tube, where the inner crushable tube reduces in axial length when a predetermined force is applied to maintain the return stroke length, and the outer crushable tube extends the stroke without increasing the axial envelope by being radially mounted around the inner tube, both constrained by the housing and piston.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single crushable tube is used to adjust stroke length, then the assembly can compensate for wear, but the axial envelope increases with stroke length
Solution Approach 1:
The patent employs nested crushable tubes where an inner crushable tube is positioned within an outer crushable tube. Both tubes share the same axial space, allowing the assembly to achieve longer stroke adjustment capability without proportionally increasing the axial envelope. The inner tube provides primary adjustment while the outer tube provides additional adjustment capacity, effectively nesting multiple adjustment functions within a compact axial footprint.
2Reliability
If the stroke length is increased to accommodate wear, then the clearance compensation is improved, but the engagement time increases
Solution Approach 1:
The adjuster assembly is segmented into multiple independent crushable tubes (inner and outer tubes) that can crush sequentially or simultaneously. This segmentation allows the system to compensate for wear-induced clearance through controlled crushing of these segments, maintaining the piston's retracted position without requiring excessive stroke length, thereby reducing engagement time while preserving clearance compensation capability.
3Extent of automation
If a mechanical tube expander adjuster is used, then automatic adjustment is achieved, but the device complexity increases
Solution Approach 1:
The patent employs crushable tubes made from materials designed to deform permanently under controlled conditions. These tubes act as disposable adjustment elements that crush once to provide automatic stroke adjustment, eliminating the need for complex mechanical expander mechanisms. The simplicity of the crushable tube design reduces device complexity while maintaining automatic adjustment functionality.
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 allows for automatic adjustment of the piston stroke length to compensate for wear without increasing the assembly's axial size, maintaining the correct clearance and engagement time, and enabling longer strokes within the same envelope, thus enhancing the reliability and efficiency of the brake system.
Implementation Method 1
The inner and outer crushable tubes are configured to each form a crushed body of reduced axial length compared to the axial length of the tube when a predetermined force is applied to the tube
Data Source
Figure 1
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Figure 3A~3B
AI summary
A piston assembly (30) for engaging two selectively engageable parts comprising: a housing defining a piston cylinder (32); a piston (31); and an adjuster assembly (50) comprising: a piston stroke limiter (70) configured to limit the length of a return stroke of the piston (31) from an extended stroke position and a retracted stroke position, the piston stroke limiter (70) comprising a spring (52) and a spring guide (53); and an inner crushable tube (60), acting between the piston (31) and the piston stroke limiter (70), the inner crushable tube (60) being arranged to reduce in axial length when a length of an extension stroke exceeds a length of a retraction stroke to maintain the length of the return stroke; wherein the inner crushable tube (60) comprises an inner crushable thin-walled tube surrounding at least a portion of the piston (31), the adjuster assembly (50) further comprising an outer crushable tube (80) mounted around and radially outwards of the inner crushable tube (60) on a tube support, an end of the tube support connected to an end of the inner crushable tube (60), the inner and outer crushable tubes (60,80) configured to each form a crushed body of reduced axial length compared to the axial length of the tube when a predetermined force is applied to the tube.