Rail Brake Control Valve Sleeve Flow Gap Design
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Solution Overview
Problem
Existing control valves for rail vehicles face challenges in controlling the flow cross-section for brake cylinder filling, leading to rapid braking times that can cause dangerous longitudinal forces, and require complex seals that wear out quickly, reducing reliability and service life.
Innovation Solution
A pneumatic control valve design featuring a piston rod with longitudinal and transverse bores, surrounded by a displaceable sleeve forming an annular gap, allowing for adjustable brake cylinder filling times and reducing wear and friction, with the sleeve being axially displaceable and connectable to a mechanical device for external actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a complex seal system is used to control the flow cross-section for brake cylinder filling, then the brake application can be controlled, but the seals wear out quickly reducing reliability and service life
Solution Approach 1:
The invention extracts the sealing function from the piston rod and transfers it to the sleeve component. The sleeve is fixed to the housing and provides sealing surfaces for the compressed air supply, eliminating the need for seals on the moving piston rod. This extraction of the sealing function to a stationary component resolves the contradiction by eliminating wear on moving seals while maintaining flow control capability.
Solution Approach 2:
The sleeve acts as an intermediary component between the compressed air supply and the piston rod. It provides the necessary sealing function and flow control without requiring seals on the moving parts. The sleeve mediates the interaction between the stationary housing and the moving piston rod, enabling wear-free operation while maintaining reliable brake application control.
2Speed
If the brake cylinder filling time is reduced for rapid braking response, then braking response is improved, but dangerous longitudinal forces are generated in the train
Solution Approach 1:
The invention makes the flow cross-section dynamic by allowing the piston rod to move within the sleeve. As the piston rod moves during braking, it progressively closes off the compressed air supply through the annular gap between the piston rod and sleeve. This dynamic adjustment of the flow area enables rapid initial braking response while automatically limiting the total air supply to prevent excessive longitudinal forces in the train.
Solution Approach 2:
The invention changes the flow parameter (cross-sectional area) dynamically during the braking process. The annular gap between the piston rod and sleeve provides an initially large flow area for rapid brake application, which automatically reduces as the piston rod moves. This parameter change enables the system to achieve rapid response while preventing dangerous longitudinal forces through automatic flow limitation.
3Productivity
If seals are used to control the compressed air supply through bores in the piston rod, then flow control is achieved, but friction and wear increase reducing service life
Solution Approach 1:
The invention extracts the sealing function from the moving piston rod and assigns it to the stationary sleeve. The sleeve provides sealing surfaces for the compressed air supply bores, eliminating the need for seals on the moving piston rod. This extraction resolves the contradiction by maintaining flow control capability through the sleeve's sealing surfaces while eliminating friction and wear on moving seals, thereby extending service life.
Solution Approach 2:
The invention replaces the mechanical seal system on the piston rod with a wear-free pneumatic flow control mechanism. The compressed air supply is controlled through the annular gap between the piston rod and sleeve, eliminating the need for mechanical seals. This substitution maintains flow control capability while eliminating friction and wear, resolving the contradiction between productivity and reliability.
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 enables wear and friction-free operation, allows for easy adaptation to changing brake cylinder filling requirements, and ensures consistent brake application across the train, reducing dangerous longitudinal forces and extending the service life of the control valve.
Implementation Method 1
the piston rod is surrounded by a sleeve which forms an annular gap to the piston rod in the initial position of the piston rod
Implementation Method 2
When braking, the pressure in the main air line is reduced. Accordingly, the pressure S present at the control piston also falls, while the opposite reference pressure A remains essentially unchanged. The resulting movement of the control piston against the compression spring causes the inlet valve to open.
Data Source
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AI summary
The invention relates to a control valve for automatic compressed-air brakes for generating a brake cylinder pressure in at least one connected brake cylinder (4) in accordance with a pressure difference between a pressure in a connected main brake pipe (L) of a train and a stored reference pressure (A), comprising a main part (1), a pipe part (2) and a support (3) having a pipe for the additional venting of air (KZE) leading from the pipe part via the support to the main part, the main part (1) comprising the following parts: a control piston (7) having a piston rod (16), said control piston being subjected, on the one hand, to the reference pressure (A) and, on the other hand, to a control pressure (S) and at least one pressure spring (13), and a compensating piston (8) that is subjected to the pressure (C) of the brake cylinder (4) against the force of at least one pressure spring (20); and a double-seat valve (10), in which an inlet valve (103) opens via a piston rod (16) when the control piston (7) approaches and an outlet valve (101) opens when the piston rod moves away, wherein the inlet valve (103) is located in an air path from an air storage reservoir (5) in the direction of the brake cylinder (4), whereas the outlet valve (101) is located in an air path from the brake cylinder (4) to the surroundings (0), wherein the piston rod (16) comprises a longitudinal bore (27) and at least one transversal bore (28) leading into the latter, wherein the at least one transversal bore (28) is located, separated only by a free space, in the vicinity of a supply (25) of pressure (R) in the housing of the air storage reservoir (5) when the control piston (7) is in the initial position, and wherein the piston rod (16) is surrounded by a sleeve (26) that forms an annular gap to the piston rod (16) below said at least one transversal bore (28) when the piston rod is in the initial position.