Rail Brake Wedge Assembly for Consistent Spring Force
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Solution Overview
Problem
Existing rail brakes waste a significant component of stored potential energy from power springs during the initial advancement of the brake shoe into contact with the railhead, limiting the braking force and vertical displacement due to the decrease in spring force throughout the relaxation stroke.
Innovation Solution
An adjustable wedge assembly is introduced between the main power spring and the brake shoe, allowing for selective expansion in the vertical orientation to maintain consistent force application, comprising an upper block, a lower wedge, and an intermediate wedge with high-friction engagement surfaces, ensuring the full restorative spring force is utilized for braking by minimizing relaxation of the power spring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the brake shoe is advanced directly by spring relaxation, then the brake mechanism is simple, but a large component of stored potential energy is wasted during initial advancement and braking force consistency deteriorates
Solution Approach 1:
A wedge assembly is introduced as an intermediary mechanism between the brake shoe and the power spring. The wedge translates the spring's relaxation motion into controlled brake shoe advancement, allowing the spring to maintain consistent force while the brake shoe moves the required vertical distance. This mediator prevents direct spring-brake shoe contact that would cause energy waste during initial advancement.
Solution Approach 2:
The wedge assembly converts vertical spring motion into horizontal wedge movement, which then converts back to vertical brake shoe motion. This dimensional transformation allows the system to decouple the spring's force application from the brake shoe's displacement, maintaining consistent spring force while achieving the required vertical travel distance.
2Force
If the spring force is allowed to decrease throughout the relaxation stroke, then the mechanism operates simply, but the braking capacity and vertical displacement range are limited
Solution Approach 1:
The wedge assembly dynamically adjusts its position and geometry during operation. As the spring relaxes, the wedge moves horizontally and translates this motion into vertical brake shoe displacement. This dynamic mechanism allows the brake shoe to travel the required vertical distance while the spring maintains consistent force throughout the entire stroke, rather than experiencing force degradation.
Solution Approach 2:
The wedge acts as a mechanical intermediary that decouples the spring's force application from the brake shoe's displacement. This allows independent optimization: the spring can be designed for consistent force output while the wedge geometry is designed to provide the required vertical travel range, thereby increasing both braking force and displacement range simultaneously.
3Reliability
If the brake shoe is held at a selected vertical distance above the railhead, then track run-out and debris clearance are accommodated, but the spring must be held in compression requiring hydraulic force
Solution Approach 1:
The wedge assembly with high-friction engagement surfaces creates a self-locking mechanism that maintains the brake shoe at the selected vertical distance above the railhead without requiring continuous hydraulic force. The friction between wedge surfaces prevents unintended movement, allowing the system to hold position using its own mechanical properties rather than continuous external energy input.
Solution Approach 2:
Instead of using hydraulic force to actively push the brake shoe away from the railhead, the system inverts the approach by using friction-based self-locking to passively maintain the clearance position. The high-friction wedge surfaces create a mechanical lock that prevents the brake shoe from moving downward, eliminating the need for continuous hydraulic compression force.
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 enhances the consistency and range of braking force applied, allowing the full restorative spring force to be used for pressing the brake shoe onto the railhead, thereby increasing the operational range and safety of the rail brake.
Implementation Method 1
The engagement surfaces between the upper block, intermediate wedge and lower wedge are selected for relatively high coefficients of static friction
Implementation Method 2
at least one associated main power spring is correspondingly held in compression by hydraulic force acting on a piston within a cylinder
Data Source
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AI summary
An extended range, consistent force rail brake comprising an adjustable wedge assembly operatively situated between the main power spring(s) and the brake shoe(s) for selectively taking up the vertical distance that the brake shoe is required to travel between the brake release position and an initial railhead contact position. The adjustable wedge assembly is thus selectively expandable in the vertical orientation, and may comprise: an upper block that is operatively connected, either directly or indirectly, to the power spring; a lower wedge rigidly affixed to a replaceable brake shoe; and an intermediate wedge that is located by suitable bearings and/or linkages for transverse, generally horizontal slidable engagement between the upper block and the lower wedge. Each of the upper block and lower wedge elements of the wedge assembly are, respectively, located by suitable bearings and/or linkages for generally vertical translational motion (but very little, if any, lateral or longitudinal horizontal motion) within upper and lower guides provided on a frame of the rail brake.