Overspeed Brake Shear Pin Cushioning
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Solution Overview
Problem
Current safety brake mechanisms for elevators fail to adequately address the damage caused by sudden deceleration during unexpected falls, as the force required to stop the lift car increases over time, potentially harming occupants and damaging the system.
Innovation Solution
An overspeed brake system that engages a safety cable when a threshold speed is reached, featuring a telescoping shaft and brake engagement device with a shear pin or spring mechanism to absorb excessive forces, allowing the lift car to drop a predetermined distance before engaging the primary brake system, thereby reducing the impact on the brake lever and components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the primary brake system is engaged immediately upon cable failure, then the lift car is stopped quickly, but the sudden deceleration causes damage to the lift car system and occupants
Solution Approach 1:
The patent applies beforehand cushioning by positioning the safety brake mechanism below the lift car to absorb impact energy before the primary brake system engages. The safety brake acts as a cushion that reduces the sudden deceleration forces, protecting both the system and occupants from damage while still achieving effective stopping
2Duration of action of moving object
If the safety brake engages after a longer fall duration, then the force required to stop increases, but the brake system must absorb greater forces
Solution Approach 1:
The braking process is segmented into two phases: first the safety brake engages to provide initial deceleration and absorb impact, then the primary brake system engages to complete the stopping. This segmentation allows the fall duration to extend slightly while keeping the force required at each stage within manageable limits, as the safety brake reduces the velocity before the primary brake engages
3Reliability
If the safety brake mechanism is added as a backup system, then occupant protection is improved, but the complexity of the braking system increases
Solution Approach 1:
The safety brake mechanism serves as an intermediary between cable failure and primary brake engagement. It mediates the transition by providing initial deceleration and impact absorption, making the overall system more reliable without requiring complete redesign of the primary braking system
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 system effectively reduces the force applied to the brake lever and components during emergency braking, minimizing damage and enhancing occupant comfort by cushioning the braking impact, thus prolonging the lift car's functionality and safety.
Implementation Method 1
The brake engagement device may comprise a rod and spring positioned within one or more brackets attached to the vertical shaft. The spring may have a compression force of at least 70 pounds, as an example.
Implementation Method 2
The brake engagement device may comprise a connecting element linking the outer and inner rails, as well as a shear pin linking the outer/inner rails and connecting elements so as to prevent an adjustment to the length of the telescoping shaft until a breaking point of the shear pin is met.
Data Source
AI summary
An overspeed brake system is described to engage a safety cable and subsequent brake system once a threshold speed is reached. An overspeed safety kit may be installed on an elevator system or lift car, to identify a threshold speed and engage a brake lever to activate a braking system. One or more brake engagement devices may be applied to limit the force on the brake lever during a fall, thereby preventing potential damage to brake components, while cushioning the deceleration.