Spring Brake Piston Tube Assembly With Dual-Material Running Nut Guide
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Solution Overview
Problem
Existing piston tube assemblies for spring brake actuators face complex manufacturing procedures and layouts, leading to increased costs and potential performance issues due to the need for intricate molding or machining.
Innovation Solution
A piston tube assembly comprising two distinct tubular bodies of different materials, where a polymer tubular body with a low friction coefficient is encased in a stronger steel tubular body, allowing for improved torque transfer and fluid transport through an internal breather valve, with connections via torque-transmitting or non-positive engagement methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a monolithic tubular body is used for the piston tube, then structural integrity is maintained, but manufacturing complexity and cost increase due to complicated molding or machining procedures
Solution Approach 1:
The piston tube is divided into two separate tubular bodies: an inner tubular body and an outer tubular body. The inner tubular body can be manufactured using simpler processes (such as injection molding for polymer materials), while the outer tubular body provides structural support. These segmented parts are then assembled together, avoiding the need for complex monolithic manufacturing processes while maintaining overall structural integrity.
2Reliability
If a single-material tubular body is used, then manufacturing is simpler, but functional performance is compromised due to inability to distribute different functionalities among materials
Solution Approach 1:
The invention employs composite construction by combining two tubular bodies made of different materials. The inner tubular body may be made of polymer material with low friction coefficient for improved running nut guidance, while the outer tubular body is made of metal material for structural strength and torque transmission. This composite approach allows each material to contribute its optimal properties to the overall system performance.
Solution Approach 2:
Different sections of the piston tube assembly are assigned different materials based on local functional requirements. The inner tubular body region that contacts the running nut uses low-friction polymer material, while the outer region requiring high strength and torque transmission uses metal material. This localized material assignment optimizes functional performance without unnecessarily complicating the entire structure.
3Ease of operation
If a polymer tubular body is used for low friction, then slidable guiding of running nut is improved, but torque transfer capability is reduced compared to metal
Solution Approach 1:
The torque transfer function is separated from the low-friction guiding function by dividing the structure into two tubular bodies. The inner polymer tubular body provides low-friction surfaces for smooth running nut movement, while the outer metal tubular body provides high-strength torque transmission paths. This functional segmentation allows each component to excel at its primary function without compromise.
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 reduces manufacturing costs while maintaining or enhancing functionality, with improved slidable guiding of the running nut and efficient fluid transport, resulting in a cost-effective and performance-enhanced piston tube assembly.
Implementation Method 1
The polymeric tubular body has the advantage of having a low friction coefficient, which leads to an improved slidable guiding of the running nut of the mechanical release mechanism
Implementation Method 2
an internal breather valve mounted to the piston tube assembly for allowing fluid transport into and out of the piston tube and any volume in fluid communication therewith
Implementation Method 3
the second tubular body preferably engages the first tubular body in a torque-transmitting connection, in particular in a positive connection such as by mutually engaging mating geometries, such as groove and tongue, or snap-fit connectors
Data Source
AI summary
A piston tube assembly (17) for a spring brake actuator (1) includes a first tubular body (35) having a contoured inside surface profile (55) for non-rotationally guiding a running nut (21) of a mechanical release mechanism (19, 21), and an internal breather valve (41) mounted to the piston tube assembly (17) for allowing fluid transport into and out of the piston tube assembly and any volume in fluid communication therewith. The piston tube assembly (17) includes a second tubular body (37) that is of a different material than the first tubular body (35), which encloses the first tubular body (35) and mechanically supports the first tubular body (35), and the internal breather valve (41) is mounted to the first tubular body (35).