Piston-Type Air Brake Actuator Sealing and Articulation
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Solution Overview
Problem
Existing air brake actuators for heavy commercial vehicles are bulky, constrain vehicle suspension and brake housing design, have limited diaphragm life, require complex sealing, and face issues with piston jamming and contamination ingress.
Innovation Solution
A piston-type air brake actuator with a cylinder of uniform cross-section, a compliantly sealed piston, and a pushrod secured to the piston for pivoting engagement with the operating shaft, along with a self-supporting operating shaft insert and pushrod insert for improved sealing and reduced contamination risk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rigid piston is used in a piston-type actuator, then sealing effectiveness is improved, but the piston may lock or jam during operation
Solution Approach 1:
The patent applies parameter changes by modifying the physical state of the piston seal from rigid to compliant. The piston is equipped with a compliant seal element that can deform and adapt to the cylinder wall, maintaining effective sealing while allowing smooth movement. This changes the mechanical properties of the sealing interface, enabling the piston to conform to surface irregularities and prevent jamming while maintaining air-tight separation between pressure zones.
Solution Approach 2:
The patent implements dynamics by making the piston seal compliant rather than rigid. The compliant seal can dynamically adapt its shape and position in response to operational conditions, pressure differentials, and surface variations. This dynamic characteristic allows the seal to maintain continuous contact with the cylinder wall during piston movement, preventing contamination ingress while avoiding the locking issues associated with rigid seals.
2Force
If the pushrod is rigidly connected to the piston, then force transmission is improved, but the actuator size and weight increase
Solution Approach 1:
The patent employs flexible shells and thin films by using a thin-walled piston structure that maintains structural integrity while minimizing mass. The piston wall is designed with sufficient thickness to withstand pressure differentials and transmit forces effectively, yet thin enough to reduce overall actuator weight. This approach allows the piston to function as both a sealing barrier and a force transmission element without requiring heavy reinforcement.
3Reliability
If a deep piston is used to prevent locking, then operational reliability is improved, but the actuator becomes bulkier
Solution Approach 1:
The patent applies parameter changes by transitioning from a deep, rigid piston design to a shorter piston with a compliant seal. The compliant sealing mechanism provides the necessary reliability to prevent locking and jamming without requiring increased piston depth. This parameter change in sealing approach allows for a more compact actuator volume while maintaining operational reliability.
4Stress or pressure
If the non-pressurized side is vented to atmosphere, then pressure equalization is improved, but contamination ingress risk increases
Solution Approach 1:
The patent uses flexible shells and thin films by implementing a sealed piston design that prevents atmospheric contamination from entering the actuator interior. The piston seal creates an effective barrier that isolates the internal components from external contaminants while still allowing pressure equalization to occur through controlled mechanisms, preventing both over-pressurization and contamination ingress.
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 solution reduces the actuator's size and weight, enhances sealing integrity, prevents contamination, and allows for a lighter return spring, increasing the brake's operational life and efficiency.
Implementation Method 1
The piston is provided with a compliant peripheral seal to permit articulation of the piston as the pushrod engages the operating shaft during pivoting motion of the operating shaft
Implementation Method 2
Pressurized air is introduced into one of the sections, and the pressure differential causes axial movement of the pushrod
Data Source
AI summary
A piston-type air brake actuator includes a cylinder having an internal sliding surface of substantially uniform cross-section, a piston dimensioned to have a substantially air tight, axially slidable fit within the cylinder, and a pushrod rigidly secured to the piston for engagement with a pivoting operating shaft of a disc brake. The piston is provided with a compliant peripheral seal to permit articulation of the piston as the pushrod engages the operating shaft during pivoting motion of the operating shaft.